Maryland has an open seat in the U.S. Senate up for election this year that’s drawing national attention, with control of the chamber hanging in the balance. That means there’s plenty of polling, as the candidates and other interested parties search for indications of which way voters will go.

The Democratic front-runners are Prince George’s County Executive Angela Alsobrooks and U.S. Rep. David Trone. The winner of the primary will likely face former Gov. Larry Hogan, who is the top candidate in the Republican primary.

The Baltimore Banner will keep a running compilation of polling. We’ll summarize recent polls, tell you what to know about how and why they were conducted — and who paid for them — and what they tell us about the state of the Senate race.

The latest poll, released on Thursday as voters already are casting ballots, put the Democratic primary race in a dead heat between Alsobrooks and Trone. Alsobrooks had 42% with Trone at 41% in the poll from Emerson College, The Hill and DC News Now.

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Emerson College-The Hill-DC News Now: Alsobrooks and Trone in dead heat

Who did the poll: Emerson College Polling conducted the poll in partnership with the two news organizations.

What the poll found: In the final days of the race, the Democratic primary is a dead heat, with Alsobrooks polling at 42% to 41% for Trone. Another 5% of those polled said they were voting for someone else and 12% were still undecided.

In hypothetical general election matchups against likely Republican nominee Larry Hogan, either Democrat would prevail: 48%-38% for Alsobrooks over Hogan; 49%-38% for Trone over Hogan.

It’s worth noting that the poll surveyed registered voters, not likely voters. Among Democrats, 11% of those polled said they were “not at all likely” or “not too likely” to vote in the primary. Another 23% had already voted and 66% were “somewhat” or “very” likely to vote.

When the poll was done: A total of 1,115 registered voters were polled between from May 6-8, with a margin of error of 2.9 percentage points. The Democratic voter sample was 462, with a margin of error of 4.5 percentage points.

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Key takeaway: Trone had been leading in all prior polling, but the Alsobrooks campaign has suggested for weeks that the race is tight. There had been no independent or internal polling to back up that claim, and now there’s evidence that this race could be very tight once all the ballots are cast.

The Alsobrooks campaign quickly promoted the poll as showing her in the lead, even though the slim 1% advantage is within the margin of error.

“This poll reflects the energy we feel at rallies and polling sites across the state: Marylanders are excited to vote for Angela because of her record and vision, and we are going to win,” Alsobrooks campaign manager Sheila O’Connell said in a statement.

It’s notable that the Alsobrooks appears to be catching up to Trone despite the massive differential in campaign spending. Trone has sunk $57 million of his own money into his campaign, while Alsobrooks has accepted donations topping $7 million. Read more.

University of Baltimore-Fox45-The Sun poll: Trone leads Alsobrooks among Dems; Hogan leads in general

Who did the poll: OpinionWorks, a polling firm based in Annapolis, conducted the poll for the University of Baltimore, Fox45 and The Baltimore Sun.

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What the poll found: In the Democratic primary, Trone leads Alsobrooks 48% to 29%, with 12% undecided. That’s a significant difference from earlier polls conducted by others that found Trone with a single-digit lead.

And if the general election were held today, Hogan would win a hypothetical matchup over either Trone or Alsobrooks. The Republican former governor leads Trone, 53%-40%, and Alsobrooks, 54%-36%.

Not surprisingly, in the Republican primary, Hogan holds a solid advantage with 69% support over his nearest rival, Robin Ficker, who polled at 9%. Another 12% were undecided.

When the poll was done: OpinionWorks conducted the poll April 7-10. The statewide sample included 1,292 likely voters across the political spectrum, with a margin of error of 3 percentage points. The Democratic sample was 600 with a margin of error of 4 percentage points and the Republican sample was 451 with a margin of error of 4.6 points.

Key takeaway: Despite Trone’s lead in the Democratic primary, Alsobrooks isn’t out of it, OpinionWorks pollster Steve Raabe told The Sun. That’s because of those who had picked one of the candidates, only 42% have firmly made up their mind. “Time is short, but she could still close this,” Raabe told the newspaper.

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Alsobrooks poll: Alsobrooks closing the gap with Trone

Who did the poll: The Alsobrooks campaign paid Garin-Hart-Yang Research Group to poll likely Democratic primary voters.

What the poll found: Trone had 43% support to 40% for Alsobrooks, with 17% undecided. The poll has a margin of error of 4 percentage points, which means that either candidate’s true tally could be 4% higher or lower. That means that the Alsobrooks campaign can make the claim that the race could be a statistical tie.

The campaign did not release full results, but made public a memo from the pollster summarizing the top line numbers.

When the poll was done: Garin-Hart-Yang questioned 600 likely Democratic primary voters between April 8-10. The campaign released the results on April 12.

Key takeaway: It’s unusual for a candidate to release a poll that shows that they’re losing. But Alsobrooks’ team is making the case that this poll shows she’s gaining on Trone and has a chance to win.

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“What this poll makes crystal clear is that David Trone has hit a ceiling and that Angela is on a path to win this race and is in the best position with the core constituencies of the Democrat base to defeat Larry Hogan,” Alsobrooks spokesperson Gina Ford said in a statement.

SurveyUSA MD Poll: Trone over Alsobrooks; Hogan over Ficker

Who did the poll: SurveyUSA is a polling company that partnered with the nonprofit Center for Election Science. the Center for Election Science describes itself as an organization focused on voting reform. In particular, the center advocates for “approval voting,” which would allow a voter to vote for multiple candidates that they “approve” of. The candidate with the most votes would still win the election.

What they found: Among Democratic voters, Trone holds an advantage over Alsobrooks, 40% to 28%, with 21% undecided. And among Republican voters, Hogan had 55% support compared to Robin Ficker at 9%, with 22% undecided.

When voters were asked to vote for “all the candidates you’d support,” all of the top candidates fell in the same order, but their numbers increased.

When the poll was done: The poll questioned 1,590 registered voters between March 13 and March 18.

Key takeaway: This appears to be the first poll that asked Republican voters about their choice in the primary. Hogan has significantly more experience, name recognition and fundraising ability than the other Republican candidates, so few have doubted that he’s the favorite to win — but now there’s data to back that up. Read more.

Goucher College-Baltimore Banner poll: Trone leads Alsobrooks; potential November matchups close

Who did the poll: Goucher College conducted the poll in partnership with The Baltimore Banner.

What they found: This poll found Trone with a lead over Alsobrooks, 42% to 33%, among likely Democratic primary voters. About 24% were undecided.

And when testing potential general election matchups, the poll found that both Trone and Alsbrooks are close to Hogan — so close, in fact, that they are within the margin of error of 3.5 percentage points. Hogan was up over Trone, 43% to 42%; and Hogan led over Alsobrooks, 44% to 40%.

When the poll was done: The survey of 800 Maryland registered voters was conducted by landline and cellphone from March 19 to March 24. The poll has a margin of error of 3.5 percentage points. The poll also surveyed 408 likely Democratic voters about the primary. Those questions had a 4.9 percentage point margin of error.

Key takeaway: Trone and Alsobrooks have both positioned themselves as the better one to beat Hogan in the general election, but this poll shows no clear advantage for any of the candidates in the fall. But there’s a long way to go, and whoever wins the Democratic primary is likely to run aggressively against Hogan. Still, Hogan remains popular, noted Goucher pollster Mileah Kromer: “Hogans popularity is so persistent because it’s broad across demographic characteristics, including steadfast Democrats.” Read more about the poll and view the data.

Washington Post-University of Maryland poll: Trone over Alsobrooks in primary; Hogan leading both in general

Who did the poll: The University of Maryland’s Center for Democracy and Civic Engagement conducted an independent poll in the race, in partnership with The Washington Post.

What they found: Among Democratic voters, the poll found Trone with 34% support compared to 27% for Alsobrooks, with 39% of primary voters still undecided — an indication that the race is wide open.

When it comes to potential general election matchups, Hogan has an advantage over either potential opponent. Hogan leads Trone 49% to 37%, with 14% undecided. A Hogan-Alsobrooks matchup drew similar data: 50% for Hogan, 36% for Alsobrooks and 15% undecided.

When the poll was done: A total of 1,004 registered voters were questioned between March 5 and 12. The margin of error is plus or minus 3.3% for the statewide responses and plus or minus 4.5% among Democrats.

Key takeaway: Despite poll respondents showing more support for the Republican Hogan in the general election, they also said that they prefer Democrats to have control over the U.S. Senate.

A total of 55% said they want Democratic control, with 35% preferring Republican control. Control over the Senate could go either way based on election results in close contests, and Maryland could be a factor. Read more.

Trone poll: Trone widening lead over Alsobrooks in primary

Who did the poll: Hickman Analytics conducted the poll for the Trone campaign.

What they found: Among those who said they are certain they will vote in the primary, Trone leads Alsobrooks, 52% to 31%. That’s an improvement for Trone from an internal poll in January that had him with 46% to 34% for Alsobrooks.

Among likely primary voters, Trone also leads, 49% to 32%.

The poll found that Trone has an advantage among Black voters (49% to 31%) and with voters in the Baltimore region (60% to 18%), where the campaign has heavily spent on advertising.

Trone campaign manager Dan Morrocco said in a statement that the data shows his candidate with “a commanding lead” in the primary.

When the poll was done: Hickman Analytics polled 1,000 likely Democratic primary voters between Feb. 13 and Feb. 18.

Key takeaway: Trone’s camp referred to its numbers as “the only credible polling” in the race, but it’s important to remember this was a poll paid for by the campaign.

It’s worth noting that Hickman models turnout differently than other polls, estimating a higher turnout among Black voters and female voters, which could account for different results.

National Republican Senatorial Committee: Hogan leads both Trone and Alsobrooks

Who did the poll: The National Republican Senatorial Committee commissioned a poll from Ragnar Research Partners to test Hogan’s changes in the general election matchup. Ragnar has polled for Hogan before.

What they found: In general election matchups, Hogan would be ahead of Trone, 49% to 33%, and ahead of Alsobrooks, 52% to 29%.

When the poll was done: Ragnar questioned 600 likely Maryland voters from Jan. 30 through Feb. 1.

Key takeaway: This poll helped Hogan determine he has a path to victory. “A Republican is not going to win in Maryland in a landslide. It’s going to be a tough uphill fight. Is there a chance to win? Is there an opportunity to win? Is there a path to win? Absolutely,” said Russ Schriefer, a political consultant and longtime advisor. Read more.

Emerson College: Hogan tied with Trone, ahead of Alsobrooks

Who did the poll: Emerson College conducted the poll in partnership with The Hill and DCNewsNow.

What they found: In general election matchups, Hogan would be tied with Trone, each with 42%. Hogan had a lead over Alsobrooks, 44% to 37%.

When the poll was done: Emerson questioned 1,000 registered Maryland voters on Feb. 12-13.

Key takeaway: This was the first independent poll done after Hogan made his surprise entrance into the race on Feb. 9. Read more.

Blended Public Affairs and Perry, White, Ross & Jacobson: Trone leads Alsobrooks in the primary, and Hogan in the general

Who did the poll: Blended is an Annapolis public affairs firm, while Perry, White, Ross & Jacobson is one of the top lobbying firms in the state capital.

What they found: In the Democratic primary, Trone had an advantage over Alsobrooks, 36% to 31%, with 18% undecided.

The poll also tested hypothetical general election matchups, with Trone ahead of Hogan, 49% to 34%, and Hogan ahead of Alsobrooks, 42% to 36%.

When the poll was done: The poll questioned 813 likely voters in mid-November 2023.

Key takeaway: This poll was conducted when the thought of Hogan as a candidate was speculative. Trone touted the results as showing he had momentum in the race. The poll came shortly before Alsobrooks replaced her campaign manager. Read more.