Democrat David Trone has added even more of his fortune to his campaign for U.S. Senate, now totaling more than $57 million in one of the nation’s most expensive primary races this year.

Trone, the congressman and founder of the Total Wine & More retail liquor chain, committed an additional $12.4 million to his campaign fund between April 1 and April 24, according to his latest campaign finance report. Trone also sent $3.15 million to his campaign on April 29, according to another filing.

Trone has now sunk a total of $57.4 million into the race, where his chief opponent is Prince George’s County Executive Angela Alsobrooks.

Trone reported $3.7 million in the bank on April 24, prior to the April 29 infusion.

Alsobrooks, meanwhile, has about $1.9 million cash on hand. All told, since entering the race last year, she has raised about $7.8 million.

In-person early voting and mail-in voting is underway in the contest, which will determine who faces the Republican nominee — which could be former Gov. Larry Hogan — in the general election. Traditional election day voting is on May 14.

The winner will succeed longtime U.S. Sen. Ben Cardin, a Democrat who announced last spring that he would not run for reelection in 2024.

Both Trone and Alsobrooks have made an issue about how their opponent funds their campaign, in what is likely to be the most expensive race in state history. Even before the latest campaign finance reports, the race was ranked one of the most expensive in the nation by the website OpenSecrets, which tracks money in politics.

Alsobrooks has alleged that Trone is trying to buy his way into the Senate with his massive level of self-funding.

On the campaign trail, Alsobrooks has pointed to Trone’s spending as a sign of her own strength.

“This is a race like one we’ve never seen before,” Alsobrooks said at an event in Linthicum earlier this week, before the latest reports were filed. “We’ve had more than $47 million, the highest-ever spending in a primary in United States history in a Senate primary. I don’t think anybody would spend $47 million to defeat you if they didn’t think you were formidable.”

Trone, meanwhile, has criticized Alsobrooks for taking money from corporate donors and political action committees.

By self-funding, Trone says, he’s not beholden to the wishes of special interests.

“I’m here for a purpose, to change things in America, because I’m not taking money from the PACs, the lobbyists, special interests,” Trone said at the same event in Linthicum. “I’m using my money that I worked hard for.”