The mayor of Waukesha, the seat of a reliably Republican county outside Milwaukee, Wisconsin, on Wednesday endorsed Vice President Kamala Harris for president – the first time the former Republican city leader has endorsed a Democrat for commander in chief, the campaign said.

“It would be easier for me to stay quiet and vote my conscience privately, but the stakes of this election are so important that I feel compelled to publicly announce that I am voting for Vice President Kamala Harris and encourage other Wisconsinites to follow ours “We are asking our country to do the same,” Reilly said in a statement distributed by the Harris campaign.

Reilly added that former President Donald Trump posed “a unique threat to American democracy” and a second term “would be even more dangerous than the first because there would be no guardrails.”

“We cannot allow him to sit in the Oval Office again,” he said.

Milwaukee’s Fox News affiliate yesterday reported on the mayor’s endorsement of Harris, quoting him as saying he left the Republican Party after the attack on the US Capitol on January 6, 2021 and voted for President Joe Biden in 2020, but is voting still often Republican.

Wisconsin is a key battleground state that could be a deciding factor in Harris or Trump’s path to victory on election night. While Milwaukee’s voting suburbs haven’t flipped to the Democrats as dramatically as comparable non-metropolitan areas in battleground states during the Trump era, the party has gradually made inroads.

Waukesha, in particular, has long been a Republican stronghold, where Democrats have made slow gains in state and federal elections over the past two decades.

In 2000, just 32% of voters in Waukesha County voted for Democratic presidential candidate Al Gore, while in 2020, 39% of voters there supported President Joe Biden. Conversely, 65% of voters there voted for former President George Bush in 2000 and 60% of voters in Waukesha voted for Trump in 2020.

In a state that Biden won by less than a point in 2020, even small shifts in suburban counties can affect the statewide outcome.

Reilly’s support comes at a time when a wave of Republicans have thrown their support behind Harris this fall.

On Thursday, Republican former Michigan Rep. Fred Upton also endorsed Harris, saying in a statement that he had never voted for a Democrat for president “until now.”

Trump is “unfit to serve as commander in chief again,” Upton said.

Other former Republican congressmen who have endorsed Harris include Liz Cheney, R-Wyot, and Adam Kinzinger, R-Ill. Harris is also touting the support of former Republican Sen. Jeff Flake, former Vice President Dick Cheney, more than a hundred former Republican national security officials, former Georgia Gov. Geoff Duncan and others.