Chicago, Illinois - The Republican Party suffers from a "cancer" of lies, Illinois Republican Representative Adam Kinzinger said Sunday, offering an explanation of his decision not to run for re-election to Congress.

Kinzinger, one of the 10 Republicans in the House who voted to impeach former President Donald Trump following the January 6 riot at the Capitol, said Friday that he would not seek a seventh term.

"You can fight to try to tell the truth, you can fight against the cancer in the Republican Party of lies of conspiracy, of dishonesty," Kinzinger said on ABC’s This Week.

"I haven’t seen any momentum in the party move away from lies and toward truth," he said.

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Defying members of his own political party, Kinzinger volunteered to sit on the congressional committee that is investigating the deadly January 6 riot. He and Rep. Liz Cheney of Wyoming are the only Republicans on the committee.

"It’s not on Liz Cheney and I to save the Republican Party," he said on This Week.

"It’s on the 190 Republicans who haven’t said a dang word about it, and they put their head in the sand and hope somebody else comes along and does something."

Kinzinger disputed the suggestion that his decision to leave Congress was a win for the former president.

"The Republican establishment now... have held onto Donald Trump," Kinzinger said. "They have continued to breathe life into him, and so actually, it’s not handing a win as much to Donald Trump as it is to the cancerous kind of lies and conspiracy" that form the "mainstream argument of the Republican Party."

In announcing his decision, Kinzinger, an Air Force veteran, said it did not signal his departure from US politics.

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"In order to break the narrative, I cannot focus on both a reelection to Congress and a broader fight nationwide," he said in a video he posted on Twitter.

"I want to make it clear, this isn’t the end of my political future, but the beginning."