David Trone, the Potomac Democrat, has funneled an additional $4.5 million of his personal fortune into his bid to win a Maryland congressional seat, leaving him with far more in the bank than Amie Hoeber, his Republican opponent.

Trone, who has spent more than $12 million of his own money on his campaign, has $3 million on hand as he heads into the final three weeks of his race to succeed Rep. John Delaney (D) in the 6th Congressional District.

Hoeber has only $132,000 in her account, but her campaign is being assisted by two political action committees, which have spent a total of $1.4 million on her behalf in recent months.

Trone, 62, the co-founder of national liquor store chain Total Wine & More, underwent what his doctors called successful cancer surgery last month after disclosing that a tumor was found in his urinary tract.

In the six weeks leading up to his operation, a period during which he went through chemotherapy, Trone put $1.5 million into his campaign, according to campaign finance reports filed Monday. Two weeks after surgery, he loaned the campaign an additional $3 million.

Hoeber, 76, a national security consultant who served in the Reagan administration, has spent $300,000 of her money on the campaign, her reports show. It is her second attempt to win the district, which stretches from the heavily Democratic precincts of Montgomery County to more conservative Western Maryland.

Her husband, Mark Epstein, a Qualcomm executive, has contributed $400,000 to Values in Electing Women, the political action committee that has spent over $1 million supporting Hoeber. The second PAC helping Hoeber, Defending Main Street, has spent nearly $400,000.

The campaign to succeed Delaney, a three-term lawmaker who is leaving Congress to run for president, is regarded as Maryland’s most competitive House race, although Rep. Andy Harris (R-Md.) is fending off a surprisingly robust challenge from Democrat Jesse Colvin. The latest campaign reports show that Colvin has slightly outraised Harris, $1.575 million to $1.5 million, although Harris has almost twice as much available to spend.

The Democratic incumbents are overwhelmingly favored in Maryland’s other six congressional races, and their campaign finance filings reflect it. Reps. Anthony G. Brown, Elijah E. Cummings, Steny H. Hoyer, Jamie B. Raskin, C.A. Dutch Ruppersberger and John Sarbanes revealed war chests of between $492,000 (Brown) and $1.19 million (Sarbanes), while none of their challengers reported more than $8,200.

Sen. Benjamin L. Cardin (D-Md.), who is expected to easily win a third term, reported contributions of $441,566 from July through the end of September, compared with $173,225 raised by Neal Simon, a Potomac businessman who is running as an independent, and $118,339 raised by Republican Tony Campbell.

Trone’s campaign for the House is his second bid for a congressional seat. In 2016, he spent more than $12 million while losing the Democratic primary in the 8th Congressional District to Raskin, who then won the general election.

Two years later, Trone used his vast financial resources to overpower seven opponents in the Democratic primary for Delaney’s seat.

Between his two campaigns, he has spent more than $25 million, leading his opponents — from the Democrats in the two primary races to Hoeber — to accuse him of seeking to buy his way into public office.

Hoeber, in a recent interview, dismissed Trone as a man who has devoted his professional life to “selling liquor” and said: “He has nothing to offer.”

Trone, who casts himself as a pragmatist, counters that his business success shows he can achieve ambitious goals and has laid the foundation for his various philanthropic interests. He also says that his wealth allows him to eschew special interests.

“David Trone won’t take money from PACs, lobbyists, or corporations and will be an independent voice,” campaign manager Jerid Kurtz said in a statement.

In 2016, Hoeber’s husband contributed nearly $4 million to Maryland USA, a super PAC set up to boost her run against Delaney. The Democrat filed a complaint with the Federal Election Commission, alleging that Hoeber was illegally coordinating with the super PAC — a complaint that has not yet been resolved.

The 6th District, which encompasses Allegany, Washington and Garrett counties, as well as a portion of Frederick County, used to be majority Republican, until redistricting after the 2010 Census shifted a large swath of liberal Montgomery into its boundaries (the redistricting has been challenged in court). It still includes a significant minority of GOP voters, and Hoeber expects to fare well by promoting her support for Gov. Larry Hogan (R), who leads Democratic challenger Ben Jealous by double digits.

But Hoeber is campaigning at a time when another Republican — President Trump — is deeply unpopular in Maryland.

Hoeber, in a recent interview, praised the president for his handling of foreign policy, including moving the U.S. Embassy in Israel from Tel Aviv to Jerusalem and “opening a communications channel to North Korea.”

“He’s not a man I would want to spend personal time with,” Hoeber said of Trump. “I don’t like his style, but I don’t think we hired him for his style. We hired him for the results, and I think he’s getting them.”

Describing herself as a conservative on issues relating to the economy and foreign policy, Hoeber said she is personally opposed to abortion but believes women should have the right to choose — a position that puts her out of step with many establishment Republicans. “Government should stay out of it,” she said.

Despite Trone’s distinct financial advantage, Hoeber insists that her defeat two years ago positioned her for success in this election. “Now I know the district; I know the people; I know the issues,” she said. “I can tell you where the potholes are in any road in Cumberland — you want to name.”

Rachel Chason and Arelis R. Hernández contributed to this report.