Republican U.S. Rep. Ken Buck said Wednesday that he won’t seek a sixth term representing Colorado’s 4th Congressional District.

Saying he believes the Republican Party has discarded conservative principles for “self-serving lies,” Buck announced in a statement that he had decided to leave Congress because “tough votes are being replaced by social media status.”

The former federal and state prosecutor’s announcement follows months of speculation that Buck was readying a departure from Washington, leading to multiple GOP candidates floating possible candidacies for the heavily Republican seat.

Buck has repeatedly stood contrary to the national GOP’s party line this year, from criticizing a House GOP move to impeach President Joe Biden and voting to oust former House Speaker Kevin McCarthy to assailing former President Donald Trump’s insistence that the 2020 election was stolen.

Buck, a former chairman of the Colorado GOP, laid out his objections to his party’s stances in a videotaped statement posted online Wednesday morning.

“Americans are rightfully concerned about our nation’s future and are looking to Republicans in Washington for a course correction,” said Buck. “But their hope for Republicans to take decisive action may be in vain. Our nation is on a collision course with reality and a steadfast commitment to truth – even uncomfortable truths – is the only way forward.”

“Too many Republican leaders are lying to America, claiming that the 2020 election was stolen, describing Jan. 6 as an unguided tour of the Capitol and asserting that the ensuing prosecutions are a weaponization of our justice system,” he said. “These insidious narratives breed widespread cynicism and erode Americans confidence in the rule of law. It is impossible for the Republican Party to confront our problems and offer a course correction for the future while being obsessively fixated on retribution and vengeance for contrived injustices of the past.”

Added Buck: “It’s time to stop feeding popular narratives and start addressing the long-term solutions.”

In a written statement released by his office, Buck said: “To my friends in Colorado, thank you for allowing me the opportunity to serve our nation, and to serve you. I look forward to seeing you at the grocery store and the high school football game. Being your representative in Washington, DC, has been the greatest professional thrill, and highest honor, of my life.”

After an unsuccessful bid as the GOP nominee for the U.S. Senate in 2010, Buck won an open U.S. House seat in 2014 after its occupant, Republican Cory Gardner, declined to seek reelection and instead made a successful run for the state’s other U.S. Senate seat. Buck served three terms as Weld County’s district attorney from 2005 to 2011, and chaired the Colorado GOP for one term from 2019 to 2021.

The sprawling 4th District covers most of Douglas and Weld counties and the Eastern Plains. Buck won reelection last year with 61% of the vote, the largest share of the state’s three Republican House members, after easily winning a primary against an underfunded, last-minute challenger.

Last month, state Rep. Richard Holtorf, R-Akron, told Colorado Politics that he was weighing whether to challenge Buck in a primary next year.

Referring to Buck as “the Liz Cheney of Colorado,” Holtorf said he was alarmed by a series of “big mistakes” by Buck, including the incumbent’s remarks criticizing Trump and frequent appearances on national cable news shows, which Holtorf derided as “pandering to the Democrat left media.”

Other Republican politicians have been nosing around a run in the district include House Minority Leader Mike Lynch, R-Wellington; Logan County Commissioner Jerry Sonnenberg, a former longtime state lawmaker; Douglas County Commissioner Lora Thomas; former University of Colorado Regent Heidi Ganahl, who lost a bid for governor last year; former U.S. Senate candidate Deborah Flora; and former 18th Judicial District Attorney George Brauchler, who made unsuccessful runs for governor and attorney general in 2018.

Weld County Council member Trent Leisy, a former member of the Weld RE-4 School Board and self-described “die-hard supporter of President Donald Trump,” made his primary challenge to Buck official last week, joining first-time candidate and fellow Republican Justin Schrieber. Democrats Isaac McCorkle, John Padora and Karen Breslin are also running in the district.

Buck broke the news in an appearance on MSNBC’s Andrea Mitchell Reports – a venue that drew sharp criticism from Republican strategist and former state GOP chairman Dick Wadhams.

“I think it is offensive that Ken Buck would announce that he’s not running for reelection during an interview on a national cable TV show rather than returning to his district and thanking the people of the 4th CD for the honor and privilege of serving in the U.S. House of Representatives,” Wadhams told Colorado Politics.

“Bill Armstrong, Hank Brown, Wayne Allard, Bob Schaffer all returned to their state and districts to announce they were not running again and thank the people that sent them there” Wadhams said, listing prominent former Republican House and Senate members from Colorado.

“Frankly, so did Democrats,” he added. “I’m not sure there’s a precedent for this, where a member of Congress from Colorado did this on national TV rather than going home.”

Colorado Republican Party Chairman Dave Williams offered Buck a mixed send-off.

“While we strongly disagree with his most recent actions like opposing the impeachment of Joe Biden or the election of Jim Jordan as speaker, we wish him the best in his future endeavors and hope he will stop unfairly criticizing the Party he once helped lead,” Williams told Colorado Politics in a text message.

Editor’s note: This developing story has been updated.