Mitt Romney's three-state shellacking by Rick Santorum laid bare the Republican White House frontrunner's Achilles heel -- an inability to motivate the party's conservative base.
The enthusiasm gap - revealed in low overall turnout at caucuses and primaries and Romney's tepid polling numbers - could end up handing President Barack Obama a second term should it continue through the November election.
"Certainly those conservative evangelicals are not going to vote in droves for Obama, but what they could do - and what they did in 2008 - is that they could stay home," said Michael McDonald, a voter turnout expert at George Mason University. Another pitfall for Romney is low turnout among the moderate and independent voters who often decide US elections, even as the Republican primaries have attracted huge amounts of media attention, McDonald said.
"If he's not energising and exciting those people right now, there's the danger that he will lose them to Barack Obama," he told AFP.
Low turnout at the polls was mirrored in a survey released on Wednesday which found that only 54% of Republicans are "very excited" about voting in November's Presidential election, compared with 58% of Democrats.
The Public Policy Polling survey also found that 25% of conservatives are "not at all excited" to vote in November, compared to only 16% of liberals. Even among ultraconservative Tea Party voters, excitement has dropped nine points from last July to 62%. "Obviously all this could change once Republicans are settled on a nominee," Public Policy Polling said of the results, but for now Obama's prospects "are looking the best they have in quite a long time."