Traditionally used by more senior members of Congress to gain influence and build alliances, leadership PACs have become more common among new members. The PACs are especially common in the Senate, where members raise larger sums of money than in the House.

Stefan Passantino, counsel to Newt Gingrich's presidential campaign and head of McKenna Long & Aldridge’s political law team, said many of the lawmakers-elect were smart to file their paperwork before the election.

“Because of redistricting, many freshmen-elect knew they were going to win after the primary,” he said.

Pocan, who will fill Sen. Tammy BaldwinTammy Suzanne BaldwinAmerican women will decide who wins and loses in 2018 elections Grassley, Dems step up battle over judicial nominees 10 Senate Democrats are up for reelection in Trump country MORE’s (D-Wis.) vacant House seat, became the first candidate-turned-member to sponsor a leadership PAC. He said he was surprised the name “Blue Majority” had not been taken and decided to make it his own.

The leadership PAC gained official status on Sept. 21, more than six weeks before the election. DeSantis, Wagner, Kilmer, Salmon and Williams followed suit in October.

Pocan said he was focused on helping people and making the steps necessary to regain a Democratic House majority, “even before day one.”

And he has a running head start: New campaign finance reports released Thursday revealed that Blue Majority PAC raised more than $33,000 since its inception.

Michael Kelly, who is helping Kaine's transition team, said the Virginia Democrat promised voters "to break through the Senate’s recent gridlock and address our nation’s challenges." He said the senator-elect will use his leadership PAC — called Common Ground — to "support others who share his commitment" to bipartisanship.

Wagner, the Missouri Republican elected to represent the 2nd district, began her leadership PAC — Ann PAC — on Oct. 9. It has not yet raised any funds, according to the FEC, but spokesman Christian Morgan said she used her campaign committee to support her colleagues during the election.

“[The leadership PAC] is a continuation of what she’s done already,” he said.  “[The money will go to] expand the Republican majority, that’s it. That’s what she hopes to accomplish.”

An analysis by The Hill in October showed that about 70 members of the 2010-elected freshman class had started leadership PACs.

Bob Biersack, a senior fellow at the Center for Responsive Politics and former FEC official, told The Hill in October that leadership PACs have become part of the “infrastructure of politics."

Passantino, the political law and campaign expert, agrees.

“Given the accessibility donors have to super-PACs and other tax-exempt groups, it makes a great deal of sense to give one’s ‘maxed out’ donors another avenue to contribute to that the member,” he said.

— Kevin Bogardus contributed to this report.

This story was updated at 6:23 p.m.