With recent polls showing Republican presidential hopeful Mitt Romney either trailing or at best tied with Rick Santorum in the Michigan primary, some Republican leaders are starting to get nervous.

One “prominent Republican senator” told ABC News senior political correspondent Jonathan Karl on Friday that “if Romney cannot win Michigan, we need a new candidate,” because with such a weak nominee “we’d get killed” in the general election.

He insisted that he expects Romney to eventually prevail in Michigan, but stated that “if he can’t even win in Michigan, where his family is from, where he grew up … he’d be too damaged” to run a successful presidential campaign.