By Doina Chiacu

WASHINGTON (Reuters) -The Republican Party on Friday censured Representatives Liz Cheney and Adam Kinzinger for joining Congress' investigation of the January 6, 2021, Capitol attack and Donald Trump's efforts to overturn his 2020 presidential election defeat, calling the probe an attack on "legitimate political discourse."

Cheney and Kinzinger are the only Republicans on the House of Representatives January 6 select committee. The panel is investigating who -- including people in Trump's circle -- had any role in planning or enabling the worst assault on the U.S. Capitol since the War of 1812.

The resolution censuring Cheney and Kinzinger, approved at a Republican National Committee meeting in Salt Lake City, accused them of "participating in a Democrat-led persecution of ordinary citizens engaged in legitimate political discourse."

Thousands of Trump supporters stormed the Capitol that day, smashing windows, assaulting police officers and sending lawmakers and then-Vice President Mike Pence running for their lives after Trump made a fiery speech repeating his false claims that his election defeat was the result of widespread fraud.

Friday's vote was dramatically different in tone from a statement the Republican National Committee released the day of the attack, when it said "these violent scenes we have witnessed do not represent acts of patriotism, but an attack on our country and its founding principles."

RNC Chairwoman Ronna McDaniel said Friday's resolution targeted the January 6 committee probe, which has subpoenaed a range of politicians and Trump White House aides as it tries to piece together their role in events leading to the assault.

"Liz Cheney and Adam Kinzinger crossed a line. They chose to join Nancy Pelosi in a Democrat-led persecution of ordinary citizens who engaged in legitimate political discourse that had nothing to do with violence at the Capitol," she said. She said she "condemned violence on both sides of the aisle."

The resolution passed on a voice vote as 168 members of the RNC gathered for their winter meeting. The yes votes were overwhelming, with a handful of nays, according to reporters at the meeting.

Cheney and Kinzinger voted to impeach Trump on a charge of incitement of insurrection, and they joined the seven Democrats on the panel investigating the attack.

The resolution said Cheney and Kinzinger have damaged Republican efforts to win back majorities in Congress.

The measure said the RNC will "immediately cease any and all support of them" as party members, but stops short of calling for their ouster from the party, as initially proposed. The committee uses some of its funds to help support Republican candidates in their campaigns.

Trump, who retains a strong grip over his party as the Nov. 8 midterm congressional elections draw closer, has been on the warpath against Republicans who have taken a stand against him. Republicans are trying to take control of both the House and the Senate from President Joe Biden's Democrats.

Persons Of Conscience

Both lawmakers issued statements in anticipation of Friday's vote.

"The leaders of the Republican Party have made themselves willing hostages to a man who admits he tried to overturn a presidential election and suggests he would pardon January 6 defendants, some of whom have been charged with seditious conspiracy," Cheney said, referring to the hundreds of Trump supporters accused of various crimes in the violent attack.

Four people died on January 6, and a Capitol Police officer died the next day. About 140 police officers were injured, and four later died by suicide.

Cheney said she does not recognize those in her party who "abandoned the Constitution to embrace Donald Trump," who has endorsed her challenger in the Wyoming Republican primary.

Kinzinger, who is not seeking re-election, said he has been a conservative Republican since before Trump entered politics. He vowed to continue "working to fight the political matrix that's led us to this point."

House Republican leader Kevin McCarthy, in an interview with Fox News, did not comment on the censure but criticized the House committee as purely political.

Not all Republicans are lining up against the two.

Republican Senator Mitt Romney praised Cheney and Kinzinger as honorable in a Twitter post on Friday. "Shame falls on a party that would censure persons of conscience, who seek truth in the face of vitriol," he wrote.

At least 71 Republican members of Congress transferred money last year to the campaigns of congressional Republicans, including Cheney's, that supported booting Trump from office, a Reuters analysis found.

Republican Senator Bill Cassidy came to their defense late Thursday, writing on Twitter, "The RNC is censuring Liz Cheney and Adam Kinzinger because they are trying to find out what happened on January 6th - HUH?"

(Reporting by Doina Chiacu and Steve Holland; editing by Jonathan Oatis, Aurora Ellis, and Cynthia Osterman)