With 100 days until the midterm elections, the fight for control of the House is entering a critical stretch, with both Democrats and Republicans pouring resources into key battleground districts in Pennsylvania.

House Democratic leader Hakeem Jeffries kicked off Democrats' "Fighting for an Affordable America" campaign Sunday in Pennsylvania's closely watched 7th Congressional District, joining Gov. Josh Shapiro to rally support for Democratic challenger Bob Brooks as the party pushes to win back the House.

Jeffries said Democrats would focus on lowering costs, restoring health care funding, ending the war in Iran and holding President Donald Trump accountable.

"When you put us back in charge of the United States House of Representatives, you'll get a Congress that speaks up for everyday Americans and a Congress that stands up to an out-of-control president," Jeffries said.

Republicans are launching their own campaign blitz. Freshman Rep. Ryan Mackenzie, whom Brooks is trying to unseat, is holding a 100-days-out event as the GOP works to defend its narrow House majority.

Trump has thrown his support behind Mackenzie, recently appearing at a Mack Trucks plant in the district where he urged Republicans to "win the midterms." The president has also traveled to other battleground states, using the White House spotlight to boost GOP candidates.

Republicans hope Trump's signature tax-and-spending package, the "One Big Beautiful Bill Act," along with other legislative victories, will resonate with voters. But they also face the historical challenge that the president's party often loses House seats in midterm elections, while Democrats are seeking to capitalize on voter dissatisfaction over the war in Iran and rising living costs.

Although all 435 House seats are on the ballot, analysts say fewer than 20 races are likely to decide control of the chamber. Pennsylvania is expected to play an outsized role, with Democrats targeting Republican-held districts including the 1st, 7th, 8th and 10th.

Shapiro, who is also seeking reelection, called Pennsylvania "the swingiest swing state" and said Democrats are determined to flip the House while pushing back against what he described as "chaos and cruelty and the corruption" in Washington.

House Speaker Mike Johnson is launching his own nationwide fundraising and campaign tour as Republicans try to protect their majority. The GOP currently holds a fundraising advantage, while both parties are also preparing for the impact of a recent Supreme Court ruling allowing national political parties to contribute directly to candidates' campaigns.