Editor's note: Bob Moser is the executive editor of The American Prospect and the author of "Blue Dixie: Awakening the South's Democratic Majority."
(CNN) -- As he launched into his victory speech Tuesday night after winning the fiercely fought Michigan primary, Mitt Romney proclaimed: "We didn't win by a lot, but we won by enough, and that's what counts."
In one sense, he was right. While Romney's narrow win over the insurgent Rick Santorum will be parsed to death by the pundits over the next few days -- Was the margin sufficient? Did he convince the conservative base? -- many Republicans who will vote in next week's 10 Super Tuesday contests will take note of just one thing: He won.
But he won ugly. Romney leaves Michigan the way he's left most primary and caucus states this year: bruised and diminished. Even his biggest victories, over Newt Gingrich in Florida and now over Santorum in Michigan, have come at a cost to his general-election prospects.
In Florida, Romney crushed his competitor with an expensive barrage of negative ads that left voters with no positive impression of the winner. In Michigan, he doubled down on his opposition to the auto-industry "bailout," which could doom him in November if he wins the nomination, while reinforcing his image as an out-of-touch plutocrat.
Romney continues to win delegates without winning either hearts or minds. He spoke Tuesday night of the "millions" who've joined his "cause." But after seven years of campaigning for president, he still has painted no clear picture of what that cause might be.
We can expect a whole new round of "Romney is inevitable" commentaries to recommence Wednesday. But while Santorum lost the battle in Michigan, he has not lost the war heading into the Super Tuesday contests.
If the Santorum who warmly addressed his supporters in Grand Rapids on Tuesday night had been the Santorum who zigzagged across Michigan the past two weeks, he would have almost surely been the winner. But the former senator from Pennsylvania blew a golden opportunity to upend the race by repeatedly lapsing into culture-war rhetoric -- criticizing the doctrine of church-state separation and calling President Barack Obama a "snob" for wanting to increase access to higher education.
In defeat, however, he delivered a lyrical speech that focused intently on his winning message of economic populism. He was, once again, the coal miner's grandson -- and the kind of Republican who can win the presidency during a Great Recession.
Many establishment Republicans will be reassured by Tuesday's results, which look on the surface like a return to the comforting predictability of a steady Romney march toward the nomination. But they shouldn't be too sanguine. Not only does Santorum have a good chance to rebound strongly next week -- he leads in the marquee state of Ohio -- but Michiganders showed a distinct lack of enthusiasm for the GOP field as a whole.
Turnout was low. According to exit polls, 63% of voters said they would "definitely" support the Republican nominee in November. Worst of all, less than half said they "strongly" favored the candidate they voted for, while 52% said they had reservations about the man they backed, or simply disliked the other candidate more.
The only safe bet, as this turbulent Republican campaign continues, is more turbulence. Romney may have gained a bit of what George H.W. Bush famously called "Big Mo" on Tuesday, but so far in this campaign, momentum has been a dangerous thing to have. Romney was christened "inevitable" after winning New Hampshire, only to be crushed by Gingrich in South Carolina -- after which Gingrich, full of "Big Mo," got steamrolled in Florida. Romney then had the wind at his back again, as he does now, but lost it when Santorum surprisingly swept Colorado, Minnesota and Missouri.
Now Romney's "just win, baby" campaign has surged ahead again. But his shortcomings as a candidate, and his lack of a resonant "cause," ensure that his path to the nomination will continue to be less of a coronation than a debilitating slog.
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The opinions expressed in this commentary are solely those of Bob Moser.