The Republican Party’s stranglehold on the House of Representatives may be crumbling, according to a new analysis by the Cook Political Report.

While the GOP has its largest House majority in more than eight decades, Donald Trump or Sen. Ted Cruz (R-TX) at the top of the ticket could seriously jeopardize the majority that has been built.

In its analysis of congressional races, the Cook Political Report moved 10 races Friday closer to Dem favor with the assumption that Cruz or Trump could have a major affect on down-ballot races from Virginia to California.

In a blog post Friday, analyst David Wasserman wrote “Democrats would need to pick up 30 seats, a daunting challenge given the GOP’s immense redistricting advantage and the vaporization of swing districts. But all cycle, Democrats have daydreamed about Republicans nominating an extremely polarizing presidential candidate, and suddenly it’s almost certain they will get their wish.”

According to Wasserman, Trump or Cruz at the top of the ticket could put a few kinds of districts into play for Democrats. For one, any district with a large Hispanic population could be a liability for Republicans. And, Wasserman says that “high-education” and “high-income” districts may also be more averse to Trump or Cruz.

That puts several tight races in California and Florida up for grabs.

“So many assumptions have been wrong this cycle that it’s difficult to be definitive about another: that the House majority won’t be in play in 2016,” Wasserman wrote.