WASHINGTON, D.C. — Republicans plan to pour extra money and resources into 10 congressional districts where Republican incumbents are vulnerable amid demographic changes that could swing the elections toward Democrats.

The special Republican effort, calledthe “Patriot Program,” asks party donors to direct funds to incumbent campaigns. The congressmen also get additional staff and support for more extensive advertising campaigns from the National Republican Congressional Committee, the GOP’s House campaign arm.

Three of the districts —represented by Republicans Will Hurd of Texas, John Katko of New York and Brian Fitzpatrick of Pennsylvania —went to Hillary Clinton, the Democratic nominee in the 2016 presidential race.

Aside from Hurd, three other Texans —more than any other state —are on the list. Reps. Pete Olson, John Carter and Michael McCaul each narrowly escaped tough Democratic challenges in the 2018 elections. Each represents a district on the outskirts of the state’s rapidly growing metropolitan areas.

Reps. Don Bacon of Nebraska, Lee Zeldin of New York, Fred Upton of Michigan and Southwest Washington’s Jaime Herrera Beutler, who represents Pacific County, are also on the GOP list of vulnerable districts.

Josh Blank, the manager of polling at the nonpartisan Texas Politics Project, said Republicans are playing defense in suburban districts that are seeing a big influx of younger, more diverse voters who can’t afford to live in increasingly popular and expensive city centers. Five of the nation’s 11 fastest-growing cities are in Texas, the U.S. Census Bureau reported in 2016.

According to early polling in suburban Texas districts released by the Democratic Congressional Campaign Committee, over half of respondents said they’d vote to replace their district’s Republican incumbent.

“It’s that type of growth that is making Democrats more competitive in the suburbs,” Blank said.

Many of these voters are new to Texas. More than 1 million people have immigrated to the state since 2010, many of them are highly educated and settled around the state’s metro centers, according to Lloyd Potter, the state demographer, in an op-ed in the Dallas Morning News.

Democrats have campaign operatives on the ground throughout the state and are seeking to target these younger voters in an effort to expand their majority in the House.

Brendan Steinhauser, a communications adviser to the Texas Republican Party and who worked with McCaul’s campaign last year, said that many of the 2018 election results jolted the state GOP.

Steinhauser said the party will remind new voters that a big reason they are in Texas is the state’s conservative fiscal policy and relatively low taxes that have made the state more attractive for consumers and commerce.

None of the Texas congressional offices mentioned responded to requests for comment.

David Wasserman, a House political analyst with the nonpartisan Cook Political Report, said many of the districts in Texas are “ticking time bombs” for the Republican party because of demographic changes.

The difference could be President Donald Trump. Wasserman said that many of the vulnerable Republican incumbents can bank on a large turnout of pro-Trump voters.

“The people who were missing from the 2018 election were predominantly whites without college degrees who were predominantly a pro-Trump demographic and that could protect these Republicans for another couple years,” Wasserman said.

Wasserman also said that the Texas Republican he believes is most vulnerable is notably missing from the Patriot Program list.

Rep. Kenny Marchant, whose district is just north of the Dallas-Fort Worth area, has seen a major influx of non-white voters and liberal professionals, Wasserman said. Marchant, now in his eighth House term, could be in real danger of being unseated if he faces a credible opponent, he said.

“They clearly don’t want to admit that it’s a competitive seat,” Wasserman said of why Marchant was not included on the list. “But he may be one of the most endangered Republicans in the state.”

Marchant could not immediately be reached for comment.

Other than demographics, some of the Republicans on the list are also viewed as less staunch conservative than most of their colleagues.

Last month, for instance, Fitzpatrick and Katko were among the few Republicans co-sponsoring the Equality Act, which expanded protection against discrimination because of sexual orientation or gender identity. They, along with Hurd, were among eight Republicans who joined 228 Democrats to pass the measure in the House, while 173 Republicans voted against it.

Fitzpatrick and Katko have histories of being among the least conservative Republicans.

The American Conservative Union rates lawmakers on their fealty to conservative causes, and the Republican House average in the last Congress was 77, with 48 GOP members scoring between 90 and 100.

Hurd’s lifetime rating is 70.3. His district is considered vulnerable because of its large Hispanic population. It also includes areas outside of El Paso and San Antonio.

Katko, who represents an upstate New York district, has a lifetime rating of 37.6. Fitzpatrick, who represents the Philadelphia suburbs, has a 44.36 lifetime rating. But his 24 score last year tied him for lowest on the conservative scale among Republicans with former Rep. Ileana Ros-Lehtinen of Florida.

Fitzpatrick won his district last year with 51.3 percent, and Clinton won in 2016 by 2 percentage points. It’s a district that includes working class areas and upscale suburban Philadelphia.

“He has to be very careful,” said Terry Madonna, director of the Lancaster, Pa.-based Franklin & Marshall College Poll.

What could hurt Fitzpatrick is straight-ticket voting, Madonna said. If Democrats are fired up and eager to punish Republicans, they could simply vote for everyone from the party on the ballot. But the drama over investigations of the Trump administration is not likely to be the biggest issue in the election, Madonna said. Health care and other day-to-day concerns are more likely to drive the vote.

Fitzpatrick and Katko’s offices did not respond to requests for comment.

Katko has “distanced himself to a certain degree from Trump,” said Don Levy, director of the Siena College Research Institute in New York. “He has succeeded in saying, ‘You’re voting for me,’ and he’s well enough known.”