Pay attention, young presidential candidates-to-be, this seems to be the lesson of the 2008 election so far: voters like winners.

Barack Obama's slam-dunk victory on Tuesday over Hillary Clinton in Wisconsin is the latest proof of this theory, for he's making Clinton look like Rudy Giuliani. Both the former NYC mayor and the current junior senator from New York state thought they could sit back and absorb a string of losses, just waiting for when the stars would align perfectly for them. Giuliani saw Florida as his electoral heaven. After Super Tuesday, Clinton gazed at the working-class neighborhoods of Ohio and the great plains of Texas and saw her Gettysburg. (She, of course, would be the North.) But the best-laid plans of mice and men and campaign strategists often go awry. By the time the Republican circus hit the Sunshine State, Giuliani looked like a loser; he had placed out of the money in all the previous contests--and Florida Republican voters validated that impression. And after losing eight straight contests to Obama after Super Tuesday, Clinton also had a big L on her forehead (and it doesn't stand for liberal).

One of the most interesting exit poll numbers from Wisconsin was this: of the Democratic voters who made up their minds in the four weeks prior to the election, Obama beat Clinton 62 to 37 percent. Of those who a month ago knew whom they would support, 50 percent chose Clinton over 49 percent for Obama. What changed in the past four weeks? Clinton and Obama were the same people they were in mid-January. Their resumes were the same. They each were making the same case for his or her candidacy. What had changed was that Obama had won a bunch of elections--and Wisconsin voters had gotten a chance to see him up and close and personal, given that there was plenty of time before this primary for Obama to campaign in the state.

This is--duh!--bad news for Clinton. You can't win by losing. And as the two move toward Ohio and Texas--which could end this race--Clinton has only lost more steam. (Obama also beat her in Hawaii on Tuesday.)

The morning after Wisconsin, a radio show host asked me, "What the heck can she do now?" I dunno. In Wisconsin, Hillary did it all. She went negative on Obama big-time, accusing him of plagiarism, charging him with cowardice for not adding an extra debate to the schedule, and blasting his plans for health care, Social Security, and the mortgage crisis. She went populist--which is right out of the Democratic playbook for candidates in trouble. She held events where she showed off her masterful command of policy details. And she made the same I've-got-more-experience-than-he-does case. That's everything she can do. And the voters said, No thank you.

With Ohio and Texas looming--the primaries are March 4--there's little room for improvement or change in her strategy. The cliche is that success breeds success. Success is the missing ingredient in her campaign. And there's not much she can do about that now.

To see my full report on Wisconsin for Mother Jones, click here.