The Republican candidate for governor in Wisconsin told supporters at a campaign event that if he is elected his party “will never lose another election” in the state.

Tim Michels’ opponent next Tuesday, the incumbent Democrat Tony Evers, said the comment, which was released by a left-leaning group, showed the Republican was “a danger to our democracy”.

Michels, a construction company owner, is endorsed by Donald Trump. He has repeated the former president’s lie that his defeat by Joe Biden in 2020 was the result of electoral fraud, and refused to say if he would certify results in a presidential election if he was governor and a Democrat won Wisconsin.

In a debate with Evers last month, Michels did not say he would accept the result of his own election. He later said he would.

Republican candidates in other swing states have cast doubt on whether they will accept results next week.

Fred Wertheimer, president of the non-partisan group Democracy 21, told the Guardian this week: “There’s great danger that the Trump ‘big lie’ is going to spread to states all over the country.

“If election deniers lose their elections by narrow margins we can expect that they will reject the results and refuse to accept them.”

The Wisconsin governor’s race remains extremely tight. On Wednesday, the polling website FiveThirtyEight.com gave Michels a 1.6-point lead. The Cook Report, a non-partisan outlet, rated Wisconsin a toss-up.

On Tuesday night, the Republican Wisconsin senator Ron Johnson, locked in his own tight fight with the Democrat Mandela Barnes, declined to commit to accepting that result.

“We’ll see what happens,” Johnson said. “I mean, is something going to happen on election day? Do Democrats have something up their sleeves?”

The Barnes campaign said it would accept the result.

A spokesperson for Michels said the candidate’s remark about never losing an election was not an indication the Republican would seek to thwart the will of the people.

“While revving up supporters to get out and vote, Tim was referring to winning and leading and then being rewarded by voters for doing a good job,” the spokesperson said.

An Evers spokesperson said: “Democracy is on the ballot. Tim Michels has made it clear he will do anything in his power to make it harder for Wisconsinites to vote and could even overturn the fair results of our elections if he doesn’t like the outcome.”