 -- Donald Trump and Mike Pence may be joining forces on the campaign trail in Wisconsin today, but some of Wisconsin’s most prominent Republicans are taking a pass on showing up for their Green Bay rally Friday night.

Among those not attending are Speaker of the House Paul Ryan and former 2016 candidate and Gov. Scott Walker.

Ryan’s non-appearance is unsurprising, after Trump this week withheld his endorsement of the Speaker of the House, currently engaged in a primary race to protect his seat.

Despite that decision, vice presidential nominee Gov. Mike Pence chose to endorse Ryan. “I strongly endorse his re-election,” Pence said in an interview with Fox News earlier this week. “He’s a longtime friend, he’s a strong conservative leader.”

While Trump still has not joined his vice presidential pick in the endorsement, Trump did say Thursday that he gave Pence the green light to endorse Ryan and called Ryan "a good guy.”

Wisconsin governor Scott Walker explained his absence not as a snub, but as a scheduling conflict. Walker will instead be in northern Wisconsin Friday, a region of the state that has suffered flood damage.

"I was with Mike Pence last week, I will be with Donald Trump when he comes back in the future," Walker said. "But the bottom line is I'll never ever let politics get in the way of being governor."

Still, Walker has made clear this week where he stands in the endorsement standoff pitting the party's nominee against Ryan, his longtime friend and political ally.

And perhaps no one made it clearer where the loyalty of mainstream Wisconsin Republicans lies than the Speaker of the State Assembly, Rep. Robin Vos, who penned an open letter on the day of Trump's visit that is less than welcoming.

"Welcome to Wisconsin, Mr. Trump, but let’s get something straight - we are Ryan Republicans here in Wisconsin, not Trump Republicans," Rep. Vos wrote in a letter published on the conservative Wisconsin site, Right Wisconsin.

Wisconsin senator Ron Johnson's re-election campaign has not yet responded to ABC News' request for comment on whether he will attend Friday night's rally.