Clinton leads Walker 52 percent to 40 percent in a hypothetical 2016 matchup in Wisconsin.
"I would love them and support them, but I would not participate," he said.
The former Texas governor compared a trio of potential GOP rivals to President Obama in 2008.
Unintimidated PAC is made up of former aides to the Wisconsin governor ahead of a 2016 bid.
Less than half of Indiana voters now support their governor.
After Iowa, she'll hit the Granite State next week, which helped her make a comeback in 2008.
The GOP senator donated to every member of his congressional delegation except Rep. Salmon.
But the former Republican later backed off comments he made in two TV interviews.
“I looked for the cameras,” the presidential hopeful said.
It's the latest sign the free-market Tea Party group intends to be a major player this cycle.