Democratic challengers to Republican members of Congress are reporting strong fundraising totals in a bevy of California races that could tip the balance of the House of Representatives.

Federal campaign finance records due last weekend showed that Democrats have been raking in money at a brisk pace over the last three months, which Democratic strategists say demonstrates how party members are standing up to the Trump administration and the anger over the GOP’s attempt to repeal the Affordable Care Act.

The most notable results were in the seven California districts where Democrat Hillary Clinton won in November but a Republican won the congressional race — districts that are among Democrats’ top national targets in their quest to retake the House from the GOP.

In six of those districts, at least one Democratic challenger had six-figure hauls from April through June — a benchmark that political analysts say is a sign of a robust, credible campaign. In five of the races, there were two or more Democrats who did so.

While no Republican incumbent was out-raised by her or his challenger, several Democrats in the districts were nipping at their opponents’ heels.

In the Central Valley, Rep. Jeff Denham, R-Turlock, took in $486,525, compared with $403,476 raised by Democrat Josh Harder, who was boosted by contributions from Silicon Valley tech workers.

Rep. Steve Knight, R-Palmdale, raised $245,419, while Democratic challengers Bryan Caforio and Katie Hill reported $212,941 and $168,408, respectively.

“They seem surprisingly close,” said Steve Boilard, executive director of the Center for California Studies at Sacramento State University. “Usually, incumbents are way up — you expect there to be a pretty lopsided relationship in those contributions.”

Democratic strategists note that all 14 Republican members of Congress in California recently voted for a House bill uprooting former President Barack Obama’s signature health care reform.

“The strong performances from Democratic challengers is evidence of the real grass-roots energy that we are seeing in districts across the country,” said Drew Godinich, a spokesman for the Democratic Congressional Campaign Committee.

But National Republican Congressional Committee spokesman Jack Pandol said that “California Republicans continue to out-raise Democratic challengers because California families trust them to fight for their jobs and security.”

Most of the Republicans still have significantly more cash on hand than their challengers, thanks to leftover funds from previous years. Denham, for example, reported $1,045,424 saved up, compared to Harder’s $374,972.

Another factor in the GOP’s favor could be competitive Democratic primaries. In some races, there are a half-dozen Democrats, so they could end up spending money and time attacking each other over the next 11 months.

“You can expect these Democrats to be broke by June,” said Kevin Spillane, a Republican strategist in Sacramento. “Meanwhile, the Republican incumbents will continue to build their war chests.”

Both sides can expect strong support from the national parties in the general election.

Harder, a first-time candidate, raised more than any other California Democrat running against a Republican incumbent. His $403,000 haul is almost three times what former candidate Michael Eggman, who narrowly lost to Denham last year, raised between April and June 2015.

“It’s a testament to how much energy we’re seeing,” said Harder, 30. “It seems like we’ve struck a chord with voters — and hopefully we can continue that momentum forward.”

A venture capital investor who recently moved to his hometown of Turlock after living in San Francisco, Harder has pledged not to take any money from corporate political action committees, and all of his donations so far are from individuals. About 75 percent of Denham’s fundraising total in the second quarter of the year came from PACs.

About half of the donations Harder reported came from outside the state, and the vast majority of his California donations came not from his district but from the Bay Area. His finance statements are dotted with donations from employees of Google, Uber, Airbnb and other tech firms.

Some of his more prominent supporters include Chris Hughes, one of the co-founders of Facebook and the former owner of the New Republic magazine, and Jason Wheeler, the former chief financial officer of Tesla, who both gave $2,700.

One asterisk on Harder’s fundraising: His campaign reported about $80,000 of donations earmarked for the general election. He won’t be able to use those funds until after the June primary, and would have to refund the contributions if he doesn’t make it to the “top two” in California’s primary system, in which only two candidates advance to the November election regardless of party.

A host of other Democrats are also running for Denham’s seat, although none raised more than $16,000 between April and June.

Denham’s campaign did not respond to a request for comment.

In Rep. Darrell Issa’s San Diego-area district, two challengers also got big totals. Issa raised a total of $455,207 — including $82,322 raised in conjunction with campaign PACs — while Democrats Mike Levin and Doug Applegate raised $332,113 and $279,285, respectively.

Levin’s best fundraising day was May 4, the day the House voted to repeal Obamacare, said Parke Skelton, a consultant for his campaign. “Clearly Democrats are engaged and active,” he said.

Issa’s campaign pointed out that he raised $1.2 million over the course of 2017, double Levin’s total. “I continue to be both heartened and humbled at the support we’ve seen so far this year,” Issa said in a statement.

Not all the races were quite as close. In Rep. David Valadao’s Central Valley district, Democratic challenger Emilio Huerta — who is running again after losing to Valadao, R-Hanford, in 2016 — raised a rather paltry $35,495, compared with the incumbent’s $320,005.

Rep. Ed Royce, R-Fullerton, who raised $454,739, out-raised his two competitors combined: Mai Khanh Tran raised $273,148 and Phil Janowicz raised $104,270. Royce also reported having more than $3 million cash on hand, compared to about $400,000 total between his two challengers.

Some of the strong totals, political analysts say, could be a result of new candidates going to their friends, co-workers and family in their initial fundraising round.

“The real question,” Spillane said, “will be how well they sustain it for the next year.”