Democratic Sen. Ron Wyden isn’t backing down from his collaboration with Republican Mitt Romney’s vice presidential pick.

Wyden published a paper with Rep. Paul Ryan earlier this year, listing what they called some options for stabilizing Medicare. But Wyden took flak from the left for partnering with Ryan, who at other times has advocated for policies that would gut both Medicare and Medicaid. And over the weekend, Mitt Romney described Wyden’s role as co-leading a piece of legislation with Ryan. Wyden says that’s not true.

But at a gathering of Portland Rotary members Wyden explained he’s not trying to avoid the association.

“I stand behind the paper. As I’ve tried to say in the last few days, Paul Ryan’s a good fellow,” Wyden said. “Mitt Romney is the head of the ticket, he’s in charge, he calls the shots. And I haven’t seen any evidence that he’d protect the Medicare guarantee.”

The promise that seniors who signed on for Medicare can have high-quality health care, Wyden said, is most important to him. He told the Rotarians he believes the stability of Medicare is the issue in the federal budget.

This story originally appeared on Oregon Public Broadcasting.