The campaign arm for Senate Republicans on Wednesday slammed Rep. Doug Collins Douglas (Doug) Allen CollinsVulnerable GOP incumbents embrace filling Supreme Court seat this year Georgia GOP Senate candidates cite abortion in pushing Ginsburg replacement Win by QAnon believer creates new headaches for House GOP MORE (R-Ga.) for launching a primary challenge against newly appointed GOP Sen. Kelly Loeffler Kelly LoefflerMcConnell locks down key GOP votes in Supreme Court fight Trump supporters chant 'Fill that seat' at North Carolina rally Vulnerable GOP incumbents embrace filling Supreme Court seat this year MORE.

The National Republican Senatorial Committee (NRSC) said they support Loeffler in the race and accused Collins of making it more difficult for Republicans to win across Georgia, including President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE in the 2020 presidential election.

“The shortsightedness in this decision is stunning,” NRSC Executive Director Kevin McLaughlin said in a statement, shortly after Collins’s official announcement he would run for the seat.

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“Doug Collins’ selfishness will hurt [Sen.] David Perdue, Kelly Loeffler, and President Trump. Not to mention the people of Georgia who stand to bear the burden of it for years to come. All he has done is put two senate seats, multiple house seats, and Georgia’s 16 electoral votes in play,” he added.

Collins, one of Trump’s closest House allies, had sought an appointment to the seat vacated by Sen. Johnny Isakson Johnny IsaksonGeorgia GOP Senate candidates cite abortion in pushing Ginsburg replacement Loeffler: Trump 'has every right' to fill Ginsburg vacancy before election Bottom line MORE (R-Ga.) in December. Georgia Gov. Brian Kemp (R) instead appointed Loeffler, a wealthy finance executive and GOP mega-donor, on Dec. 4, and she was sworn in earlier this month.

“The NRSC stands firmly behind Sen. Kelly Loeffler and urges anyone who wants to re-elect President Trump, hold the GOP senate majority, and stop socialism to do the same,” McLaughlin said.

The Senate Leadership Fund (SLF), a super PAC aimed at expanding the GOP Senate majority, similarly slammed Collins for entering the race and backed Loeffler.

“It’s so selfish of Doug Collins to be promoting himself when President Trump needs a unified team and Senator Loeffler is such a warrior for the President,” SLF President Steven Law said in a statement. “As we’ve said before, Senator Loeffler is an outsider like Trump, not just another D.C. politician. We’ll have her back if she needs us.”

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The Cook Political Report rates the Georgia Senate race as “likely Republican,” but Collins’s challenge could give Democrats an advantage as it sets up a campaign in which the two Republicans could spend millions of dollars targeting each other.

The Democratic Senatorial Campaign Committee (DSCC) quickly celebrated the idea of an “expensive, protracted brawl” between the GOP candidates.

“At the start of this election cycle, Republicans believed they could take this state for granted, but not anymore,” DSCC spokeswoman Helena Kalla said in a statement released after Collins's announcement.

The intraparty contest will “force unelected mega-donor Senator Loeffler and Trump ally Congressman Collins into a race to the right that reveals just how out-of-touch both are with Georgia voters,” Kalla added.

Georgia will hold a special jungle primary election on Nov. 3. The top two performers, regardless of party, will face off in a run-off election. Collins and his allies, however, are pushing for a change to state election law to create a more traditional primary in May.

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In announcing his campaign, Collins said he gave “serious deliberation” about the role he should serve to “best benefit [Georgia], the country and Donald Trump.”

A spokesperson for Collins was not immediately available for comment in response to the NRSC.

Updated at 9:24 a.m.