In the 2024 showdown for the House majority, Pennsylvania will be a key battleground.

As Republicans defend their razor-thin majority in the chamber, they'll be playing plenty of defense to try and retain GOP-held seats in the blue bastions of California and New York.

But in Pennsylvania, which holds primary elections on Tuesday, Republicans will be on offense, targeting three of the most vulnerable House Democrats in the country.

"If Democrats are to take back control of the House this November, they’ll need to hold the line in the Keystone State," Erin Covey, House races analyst for top non-partisan elections handicapper The Cook Political Report with Amy Walter, said recently.

THESE SIX HOUSE SEATS COULD FLIP FROM BLUE TO RED IN NOVEMBER

Pennsylvania Democratic Rep. Susan Wild in a House hearing

Rep. Susan Wild, D-Pa., speaks during a hearing before the Global Health, Global Human Rights, and International Organizations Subcommittee of the House Foreign Affairs Committee on Capitol Hill April 20, 2023, in Washington, D.C.  (Alex Wong/Getty Images)

Atop that list is three-term Democratic Rep. Susan Wild in the state's 7th Congressional District, which is one of the most evenly divided House districts in the country.

In flipping the seat in 2018 and in her 2020 and 2022 re-elections, Wild's races have come down to the wire. But Wild, in anticipation of another bruising re-election bid, has assembled a formidable campaign war chest, far ahead of her GOP challengers.

The GOP congressional primary is a three-way race between state Rep. Ryan Mackenzie, National Guard veteran Kevin Dellicker and attorney Maria Montero.

"Both national parties are almost guaranteed to invest in this race," Covey emphasized. "But the GOP candidates’ anemic fundraising has made some national GOP strategists less bullish on flipping this seat, and other Democratic-held swing seats could take priority in November."

Matt Cartwright, Pa. Democrat, speaking as former Gov. Tom Wolfe, D-Pa., left, looks on at

Rep. Matt Cartwright, D-Pa., speaks before President Biden takes the stage at a political event at the Marts Center Aug. 30, 2022, in Wilkes-Barre, Pa.   (Michael M. Santiago/Getty Images)

Republicans are also taking aim at Democratic Rep. Matt Carwright in northeastern Pennsylvania's 8th Congressional District. And across the state, in the Pittsburgh-based 17th District, Rep. Chris Deluzio is being targeted by the GOP.

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But neither district is expected to have competitive Republican primaries on Tuesday.

Wealthy construction company CEO Rob Bresnahan is considered the presumptive nominee in the 8th District, while state Rep. Rob Mercuri doesn’t face any major rivals in the primary in the 17th.

background image: US House chamber; inset: House Democrats with toss-up races

Six House seats held by Democrats could flip in the 2024 elections, expanding the Republicans' slim majority in the chamber. (Getty Images)

While they play plenty of defense in Pennsylvania, Democrats are also eyeing an opportunity to flip a red seat. That opportunity is in the 10th District — anchored by the state capital Harrisburg in the central part of the state — where former Freedom Caucus Chair Scott Perry is up for re-election.

Republicans control the House 218-213, with vacant seats in three red districts and one in a blue district. The Cook Report rates 22 races as toss-ups, evenly split between the Democrats and Republicans.

Republicans controlled the House majority for eight years before the Democrats won back the chamber in the 2018 midterms. In the 2020 elections, the GOP defied expectations and took a big bite out of the Democrats’ majority. The GOP narrowly won back control of the chamber in the 2022 midterms, but hopes of a red wave never materialized.

Get the latest updates from the 2024 campaign trail, exclusive interviews and more at our Fox News Digital election hub.