Much of this reflects the political reality that freshmen like Mr. Barr, particularly those from districts in which neither party dominates, are considered vulnerable. And that explains why a seat on the Financial Services Committee is so coveted.

Political action committees — set up by lobbying firms, unions, corporations and other groups trying to push their agenda in Congress — have donated more money to Financial Services Committee members in the first six months of this year than to members of any other committee. The $9.4 million total is nearly $2 million more than the total for the Armed Services Committee, the only House panel with more members.

With so many lawmakers clamoring to be on the Financial Services Committee, it has grown to 61 members from 44 since 1980, forcing the installation of four tiered rows of seats in the Rayburn House Office Building — with the first row of lawmakers on the floor, just in front of the tables used for witnesses.

The committee’s chairman, Representative Jeb Hensarling, Republican of Texas, remains the top recipient of donations from industry PACs this year, taking in $282,000, according to the Center for Responsive Politics, a nonprofit group that tracks the influence of money in politics. But three Republican freshmen — Mr. Barr and Representatives Tom Cotton of Arkansas and Ann Wagner of Missouri — have raised more money from industry PACs than many longtime committee members like Representative Spencer Bachus, an Alabama Republican who served as the panel’s chairman until the end of last year.

The imbalance is apparent on the Democratic side as well. Each of the seven freshman Democrats on the committee has raised more industry PAC money so far this year than the committee’s top Democrat, Representative Maxine Waters of California, who has had a testy relationship with the industry.

These freshman Democrats joined this year with Republicans on the committee — over the objection of Ms. Waters and the Obama administration — to support measures advocated by Wall Street banks that would roll back some of the strictest provisions of the landmark Dodd-Frank financial regulations, which were passed in 2010 in the aftermath of the global recession.