California Gov. Arnold Schwarzenegger (R) thinks Mitt Romney will win the GOP nomination for president in 2012.

Schwarzenegger predicted on the Tonight Show on Thursday night the former Massachusetts governor will emerge from what could be a crowded field.

"I think maybe Romney by a hair," he said.

Schwarzenegger also lamented that he can't run himself because the Constitution requires the president to be born in the U.S.

"I think that you're just asking me this because you know this is painful to me because I'm foreign born and I can't run for president," the governor told Jay Leno.

Schwarzenegger said he would definitely make a bid for the White House if the Constitution were amended.

"Without any doubt," he said. "There's no two ways about that."