Retiring Michigan Rep. Paul Mitchell is leaving the GOP to become an independent, he announced Monday, saying the party has taken a turn for the worse with leaders’ behavior since Election Day.

In a letter to Republican National Committee Chairwoman Ronna McDaniel and House Minority Leader Kevin McCarthy of California, Mitchell criticized the party for going along with President Donald Trump’s nonconcession after losing to President-elect Joe Biden and for launching false and misleading attacks on the integrity of the election.

“This party has to stand up for democracy first for our Constitution first, and not political considerations,” he said to CNN’s Jake Tapper, adding, “not simply for raw political power. And that’s what I feel is going on, and I’ve had enough.”

Mitchell, who was first elected in 2016 and didn’t run again this year, said that though he is leaving the party he will still endorse and assist candidates he shares views with. Mitchell said he has supported the administration most of the time and been active with the national and state party, but said it’s time to cut ties.

On CNN, Mitchell was also critical of a Republican-led attempt from Texas that challenged election results from Pennsylvania, Georgia, Michigan and Wisconsin, states key to Biden’s victory. The Supreme Court dismissed that case on Friday.

The case backed by Republican state attorneys general from Texas and 17 other states also had the support of 126 House Republicans — almost two-thirds of the current caucus, including McCarthy and Minority Whip Steve Scalise of Louisiana — who signed a brief encouraging the court to hear the case.

“Anybody that gets into politics has to be willing to accept winning and losing with some level of grace and maturity,” Mitchell said.

In his letter, Mitchell warned of long-term harm to the country if Republican leaders don’t condemn rallies by Trump supporters protesting the election results and harmful conspiracy theories.

“It is unacceptable for political candidates to treat our election system as though we are a third-world nation and incite distrust of something so basic as the sanctity of our vote,” his letter said.

Mitchell announced last year that he would not run again to spend more time with his son who has special needs.

Rep. Abigail Spanberger, a Virginia Democrat, has been voting as his proxy since the beginning of December. He said in a tweet that he and his wife suffer from severe asthma, and his physician asked him to not travel to Washington after Thanksgiving.

His reliably Republican seat based in Michigan was won in November by businesswoman Lisa McClain, who defeated state Rep. Shane Hernandez.

During his tenure in the House, Mitchell criticized Trump’s behavior several times, including when Trump posted racist tweets about four Democratic congresswomen.

The former CEO of Ross Education, a professional health care training network, said he caught heat for speaking out against the president, but argued it was the responsibility of him and others to do so. And that’s why he’s ending his tenure in Congress by speaking out again.

“Our leadership owes us better than what we’re seeing right now,” he said. “And until I see that I’m going to be an independent because it’s simply unacceptable.”