Further troubling for the presumptive favorite is that more Republicans think that rival Rick Santorum best represents their values, and that more GOP voters would "enthusiastically support" him than Romney. Even then, only a third of Republicans say they would be excited to vote for the former Pennsylvania senator, while just over a quarter would be enthusiastic about punching a ballot for the former Massachusetts governor.

Romney's core of support comes instead from the 47 percent of voters who say it's more important to nominate a candidate who can win in 2012, rather than one with whom they agree on policy. Romney is the choice of nearly half of voters when asked who is most electable.

Still, the CBS polling numbers paint a troubling picture for Republicans looking to take back the White House in 2012, who know doing so is predicated on strong turnout from the conservative base. Nevertheless, GOP leaders might be heartened by a strong Republican bench of would-be candidates — including Chris Christie, Sarah Palin, Mitch Daniels, Marco RubioMarco Antonio RubioTrump must send Russia powerful message through tougher actions McCain, Coons immigration bill sparks Trump backlash Taking a strong stance to protect election integrity MORE, Paul RyanPaul Davis RyanMcConnell: 'Whoever gets to 60 wins' on immigration Overnight Defense: Latest on spending fight - House passes stopgap with defense money while Senate nears two-year budget deal | Pentagon planning military parade for Trump | Afghan war will cost B in 2018 House passes stopgap spending measure with defense money MORE, Bob McDonnell and Haley Barbour — whom voters continue to pine for.