While the primaries in neighboring suburban counties Tuesday stole attention with victories by women and first-time candidates, the Bucks County contest between Rep. Brian Fitzpatrick and newcomer Scott Wallace, a millionaire philanthropist, is poised to be a battleground for national Republicans.

The race in Pennsylvania's First Congressional District is shaping up to be among the most expensive in the country, as Republicans seek to stem the bleeding wrought by President Trump's low approval ratings in the suburbs and a wave of retirements.

Fitzpatrick, 44, won the seat two years ago, succeeding his older brother, in the year's third-most expensive House race in the country. The candidates and outside groups spent a total of $22 million, according to the Center for Responsive Politics, a watchdog group.

"It's widely believed" that the First District campaign "will be one of the most competitive in the nation, and as a result, it should be expected that millions of dollars will be spent by both sides, perhaps as much as in 2016," said J.J. Balaban, a Philadelphia-based Democratic strategist.

At least one prominent GOP group has already signaled how important it believes the race is to retain the party's majority in the House. Last month, the Congressional Leadership Fund, a super PAC close to House Republican leaders, reserved $1.4 million in airtime for television advertising in the district. That's just the group's first installment, a spokesman said.

The group has also set up a field office on the ground in Bucks, one of 31 it has established in key districts across the country. (Congressional Leadership Fund also has an office in Western Pennsylvania's 17th District, where it's seeking to reelect Rep. Keith Rothfus.)

Spokesman Michael Byerly accused Wallace of trying to buy the seat. "CLF looks forward to exposing Wallace for who he truly is – a rubber stamp for [Nancy] Pelosi's extreme liberal agenda," he said.

The stakes in Bucks County — already a perennial battleground — grew a few months ago, when the Pennsylvania Supreme Court ruled the congressional map was an unconstitutionally partisan gerrymander. The new map imposed by the court boosted Democrats' chances to flip seats — so much so that Republican Rep. Ryan Costello announced he wouldn't seek reelection in Chester County's Sixth District.

Hillary Clinton would have won the newly drawn district by nearly 10 percentage points. That margin doubles in the Montgomery County-based Fourth and the Delaware County-based Fifth. U.S. Rep. Steve Stivers of Ohio, head of the House Republicans' campaign arm, has said it would be "really tough" to hold the Delaware County seat, from which U.S. Rep. Pat Meehan resigned last month.

Under the old map, Clinton barely carried the Costello and Meehan districts. By contrast, Trump narrowly won Fitzpatrick's old district, and the new one swung to Clinton by just a couple percentage points.

In their bid to take control of the House, Democrats are betting on anti-Trump backlash in affluent suburban districts like Pennsylvania's First, which also includes part of Montgomery County. But Fitzpatrick, a former FBI agent who has broken with the president on issues like repealing the Affordable Care Act, is expected to pitch himself as a pragmatist focused on local issues like fighting the opioid crisis.

He defeated a Trump-like opponent in Tuesday's primary.

"The voters of Bucks and Montgomery Counties are moderate and independent thinkers, which is why they overwhelmingly approve of Congressman Fitzpatrick and why they reject out-of-touch billionaires and extreme-left partisan ideologues like Scott Wallace," Fitzpatrick spokesman Mike Barley said Wednesday.

Scott Wallace, 66, won Tuesday's three-candidate Democratic primary. Some political observers have argued that his wealth — Wallace's net worth is estimated to be greater than $100 million — could create a political liability.

The House Democrats' campaign arm suggested that was in fact a sign of independence, saying that Wallace wasn't accepting money from corporate political action committees.

"Wallace has a strong record of service, promoting economic development, and fighting for veterans, and Fitzpatrick has spent his brief time in Congress representing his big donors and special interests, while leaving his constituents by the wayside," a spokesman for the Democratic Congressional Campaign Committee wrote in a memo Tuesday night.

Democrats also pointed to their party's win in a special election in the 178th state House District Tuesday as the latest evidence that Bucks County was trending blue. Helen Tai's win — albeit by less than 100 votes out of 12,600 cast — was the first for a Democrat in the district in 34 years.

For his part, Wallace said Fitzpatrick was "part of the political class that's made a mess in Washington."