Donald Trump's fourth scheduled stop in eight days in Wisconsin is a sign of his increased attention as Republicans fret about the former president's ability to match the Democrats' enthusiasm and turnout machine.

Republican Trump critic Liz Cheney made her first campaign appearance with Kamala Harris, in the Wisconsin town known as the birthplace of the GOP.

Two dozen Wisconsin Republicans, including former lawmakers, other former elected officials and a GOP sitting district attorney, have signed an open letter declaring their support for Democratic Vice President Kamala Harris in her campaign for president and condemning the Republican nominee former President Donald Trump.