Mitt Romney suffers from an enthusiasm deficit. Voters gathered at the middle school here Tuesday night went overwhelmingly for Romney -- overwhelmingly but reluctantly. This was a caucus of agonizers and nose-holders.

To the extent that this sentiment is widespread, as Romney's seemingly immovable 25 percent ceiling suggests, it poses an obstacle, although certainly not an insurmountable one.

Not to Romney's winning the nomination -- that seems inevitable. Yet the enthusiasm deficit cannot be good for Romney's general election prospects. GOP antipathy to President Obama may end up being enough of a motivator, but indifference to your own party's candidate is never a good sign.

Four years ago, at the same precinct in this fast-growing, affluent Des Moines suburb, Romney lost narrowly to former Arkansas Gov. Mike Huckabee, garnering 102 votes to Huckabee's 127.

On Tuesday night, Romney trounced his rivals. The former Massachusetts governor won 117 votes to Rick Santorum's 86. The rest of the pack didn't come close. Ron Paul had 59 supporters, Rick Perry 46 and Newt Gingrich 44. But Romney's healthy margins here -- far superior to his eight-vote squeaker statewide -- masked an underlying ambivalence, even dissatisfaction, among the dozens of voters I interviewed as they waited to caucus.

"Romney has less negatives in my opinion than all the others," said Jerry Gay, 70, a retired schoolteacher. How's that for a ringing endorsement?

Aside from a single couple who stood out with Romney insignia emblazoned on their jackets, no one I spoke with expressed anything approaching enthusiasm about his candidacy. Their votes were driven by intellectual calculation -- Romney as the best positioned to beat Obama -- not by passion for the candidate or his message.

Some who backed other candidates sighed with resignation and said they'd grudgingly pull the lever for Romney if he is the Republican nominee. They described him with phrases like "slick politician," "wishy-washy," "wavers too much" and "doesn't line up with what I believe."

Then they said their doubts about Romney's conservative bona fides were outweighed by their aversion to Obama -- his health care plan came in for particular, unprompted ire -- and their zeal for denying him a second term.

Doug Wirth, a pharmaceutical salesman, told me he was leaning toward Michele Bachmann. Asked about Romney, Wirth was categorical. "Absolutely not," he said. "He's on the bottom of my list."

And if Romney became the nominee? Wirth grimaced. "I'd support him. Anybody but Obama."

Others said even that tantalizing imperative would not be enough to overcome their distaste for Romney. "Absolutely no way," said Colleen Grace, 62, an accountant for a struggling construction company. She called Romney "way too liberal, telling us what he wants us to hear and not what he is."

General elections have a way of concentrating the mind behind a party's candidate. All those warnings about disappointed Hillary Clinton voters who would stay home in November rather than settle for Obama evaporated after the anger of the protracted primary season had a chance to subside.

Four years ago Obama inspired excitement among Democrats. Romney struggles to kindle even a flicker of such sentiment.

In the end, votes aren't weighted for intensity. An ambivalent vote counts as much as an impassioned one. But being the candidate whom voters settle for, not the one they fervently cheer, is not the healthiest place to start.