As the candidacy of Republican presidential nominee Donald Trump has taken a nose dive in recent weeks, a once unthinkable scenario has been bubbling to the surface. While Democrats had been eyeing a takeover of the Senate for quite some time, talks of Republicans losing the House — a legislative chamber where they hold one of the biggest majorities since before the New Deal — have started.

The prospects, to say the least, are pretty slim at this point. While Trump trails Clinton by 5.2 points nationally in averages of national polls compiled by Real Clear Politics, a national map of gerrymandered districts favorable to Republicans and a whopping current margin of 60 seats in the House mean that Democrats would have to have historic election results to win back a majority.

That said, it is theoretically possible. The Cook Political Report, an independent newsletter that analyzes elections and campaigns in American politics, has listed 30 seats in the House currently held by Republicans that are either a tossup or only leaning toward Republicans (there are five Democratic seats that are leaning Democrat or a tossup at this point). Should Democrats find a way to capitalize on all of those seats it would be enough to swing the House from its current makeup — 246 Republicans vs. 186 Democrats — to a 216-216 tie. Three current vacancies would then be in play to decide the majority.

Here are five of the most competitive districts held by Republicans.

New Jersey’s Fifth District: Republican Rep. Scott Garrett is facing what some analysts say is the toughest race of his career, according to the New York Times. After comments last year that he wouldn’t donate to his party’s campaign committee because it recruits and supports gay candidates, Democrats have capitalized on the opportunity with challenger Josh Gottheimer, a former Clinton speechwriter.

Florida’s Seventh District: Republican Rep. John L. Mica, who has held this seat for more than two decades, is facing a tough campaign against Stephanie Murphy, a business professor and former national security specialist. Murphy, whose family immigrated to the United States from a Vietnamese refugee camp, has attracted $962,000 worth of support from the House Majority PAC, a super PAC that supports Democrats in House races.

Virginia’s 10th District: First term Rep. Barbara Comstock, a Republican, was forced into an uncomfortable position recently after a video showing Trump bragging in 2005 about sexual assault surfaced: She had to abandon her party’s presidential nominee. Her race against Democrat LuAnn Bennet, a real estate developer, has become very close in the final weeks before Election Day.

Nevada’s Third District: You have to feel for Nevadans. As a swing state for both the presidential election and the Senate election, this year the state has been the target of massive amounts of political ad spending. In the third district, which was left open after Republican Rep. Joe Heck left to run for the Senate, Democrat computer programmer and consultant Jacky Rosen and Republican businessman Danny Tarkanian are in a tight competition that has attracted $6.8 million of spending between both parties and outside groups interested in the seat.

New York’s 24th District: Here is an example of another first-term Republican struggling in the shadow of Trump. Rep. John Katko is defending his seat in a district that includes Syracuse, a city that is pretty Democratic for upstate New York. He’s competing against Colleen Deacon, a former regional director for Democratic Sen. Kirsten Gillibrand.