Barack Obama could be excused for believing two weeks ago that he had nothing more than a flower-strewn path to the nomination. Women fainted in his presence, the media loved telling the story of the new Bobby Kennedy, and Hillary Clinton appeared to have all but conceded in her last debate. A funny thing happened on the way to Obama’s coronation, however — suddenly people started treating him as a candidate rather than a secular messiah, and Obama displayed a surprising glass jaw.

Now he faces an unexpected stumble, losing three of four primaries after a string of victories that should have convinced people the primaries were over. He has to fight a two-front war while both Hillary and John McCain work in parallel to derail him:

With losses in three out of four primaries yesterday, Sen. Barack Obama (D-Ill.) and his campaign face a scenario that a barrage of advertising, phone calls and door-knocking could not avert — a protracted, two-front war against Sen. Hillary Rodham Clinton and the presumptive Republican nominee, Sen. John McCain.

Even before the polls opened, campaign officials were dreading an outcome that would keep Clinton (D-N.Y.) in the race at least through the Pennsylvania primary on April 22. Those seven weeks will cost Obama at least $10 million, and possibly much more, campaign aides say, as he battles a rejuvenated Clinton who will have every incentive to try to force him into a major mistake. …

McCain has already made clear how he will try to brand Obama if they are opponents in November, drawing on the Illinois Democrat’s Senate votes on abortion, taxes and guns as evidence that he is out of the mainstream. But more broadly, Republicans are poised to offer what they consider a stark contrast between McCain’s lifetime of experience — in war, in the Senate, in politics — and a caricature of a young, inexperienced neophyte with little but fancy rhetoric to offer.

That is a line of attack Clinton has tried for weeks. But McCain’s advisers say they think their candidate will be more effective in convincing the public that Obama is not ready to lead the nation, especially during an economic downturn and while waging two wars overseas.

As part of the wide-ranging case they have begun constructing, they plan to follow some of the threads that Clinton has already exposed: Obama’s ties to Chicago businessman Antoin “Tony” Rezko; the senator’s failure to hold hearings on Afghanistan in his Senate Foreign Relations subcommittee; his decision to repeatedly vote “present” in the Illinois legislature.

Of course, Obama had faced a two-front battle for the last month. Ever since Super Tuesday on February 5th, John McCain knew he had the Republican nomination sewn up. Even that night, his speech targeted Barack Obama instead of his GOP rivals, and McCain has focused on Obama almost exclusively. Presciently, he dropped the attacks on Hillary Clinton that he and other Republicans had used during the debates.

So what’s changed? Hillary Clinton decided to go negative over the past two weeks. Everyone expected her to do it, but no one knew it would be as effective as it has been. Many analysts wrote it off as a desperation tactic, and that had some truth to it; if she had been winning some of the states in February, she likely wouldn’t have risked it. However, Obama has some glaring deficiencies, and Hillary’s team has managed to highlight them without alienating voters, who generally like Obama.

Even then, it wouldn’t have mattered if Obama had handled the negative campaigning with any kind of aplomb. Instead, his campaign made a serious unforced error over NAFTA and essentially got caught in a series of lies over their outreach to Canadian diplomats. That undermined Obama’s political integrity, his greatest asset. He also got caught up in the expected media feast of the Tony Rezko trial, an opporunity for the press to look a little more like journalists than hagiographers.

And how did Obama react? He blew up during a Texas press conference heavily attended by Chicago journalists. He stormed off after only eight questions regarding the contacts between his campaign and Canadian diplomats over NAFTA and the Rezko trial. The national press had already been grumbling about his insularity, and Obama gave them an excuse to write reams of material about it, Rezko, and the NAFTA dance.

In short, Obama has exposed himself as a seriously inexperienced and flawed candidate. He hasn’t really been tested until now, and the glass jaw he showed in the first few days of the real bout must have the party establishment worried about a lengthy battle against either Hillary or McCain. Against both, he may soon flounder — and that slim lead in pledged delegates will not present much of an obstacle to bypassing him in Denver.

UPDATE: Added the Hot Seat poll. For AOL readers, welcome to Hot Air — take a tour of the site, and keep checking back with us. We update a lot here, so be sure to bookmark us for regular reading!

UPDATE II: Michael Graham predicted this five weeks ago, although not the part about not winning another state.