Republican critics of Donald Trump have raked in campaign cash this year as their votes to impeach the former president and investigate the Jan. 6 Capitol attack have put them in the crosshairs of Trump and his allies.

Why it matters: The 2022 midterms won't just determine which party controls Congress. They're also shaping up to be a test of Trump's continued hold on the GOP. The few remaining Republican dissenters in Washington need to put up big fundraising numbers if they hope to stave off a purge.

• Two prime Trump antagonists, Reps. Adam Kinzinger (R-Ill.) and Liz Cheney (R-Wyo.), were front and center this week as the sole Republicans on the House select committee investigating the Capitol attack.
• It earned them the fury of Trump's many Republican allies, but they — and a larger cohort of Trump-skeptical Republicans — are building huge political war chests nonetheless.

What's new: Americans Keeping Country First, a super PAC created in late February to defend Republicans who voted to impeach Trump this year, is set to report $525,000 in income through the end of June, the group tells Axios.

• That puts it on or above the fundraising pace of independent political groups going after the few remaining Republican Trump critics in Congress.
• One such pro-Trump group, Drain the DC Swamp PAC, brought in a little over $600,000 during the first half of the year.
• And America Strong PAC, which formed in early May to attack the 10 House Republicans who voted for impeachment, raised $51,000 during its first two months.

What they're saying: "The strong start for Americans Keeping Country First reflects the broad support for the Republicans who voted to put country first," Brendan Buck, a senior adviser to the group, told Axios in an emailed statement.

• "These members stood on principle and now we are prepared to stand with them."

Cheney and Kinzinger themselves are also putting uphuge fundraising numbers for the first six months of an election off-year.

• Cheney raised more than $3 million in the first half of the year. She has $2.8 million cash on hand.
• Kinzinger's campaign raised nearly $2 million, and ended June with more than $3 million in the bank. His leadership PAC raised more than $1.5 million, according to a Federal Election Commission filing on Thursday.
• That leadership PAC has also steered cash to Cheney and seven of the other Republicans who voted to impeach Trump in January.

The big picture: Their votes for impeachment and the Jan. 6 select committee have cost both members support with the national Republican base and its media allies. A recent survey showed Cheney 43 points underwater with GOP voters.

• They're also substantially outraising their intra-party competition.
• Former Trump Commerce Department official Catalina Lauf, Kinzinger's most well-funded Republican primary opponent raised just over $350,000 from the start of her campaign in February through June.
• Cheney's top challenger, Wyoming state Sen. Anthony Bouchard, brought in about $550,000 through the end of June.

Yes, but: It's not just Trump allies or independent spenders Kinzinger faces, it's Trump himself — and a political operation that's raised $75 million this year.

• The former president has singled out Kinzinger as one of a handful of "RINO losers" who "are what’s really wrong with the Republican Party."