Former Vice President Al Gore's surprise endorsement of Gov. Howard Dean is definitely just what the Doctor ordered, giving him some extended "buzz," some nice joint appearances, and some serious street cred among political professionals and the chattering classes of Washington. Indeed, much of the Democratic establishment is rushing to crown Dean as the nominee.

But let's remember: nobody's voted yet. Dean's got a ways to go in persuading a majority of Democrats that he's the guy. And as the self-described "people-powered" candidate, he should be the last candidate around to want any sort of coronation by the Democratic establishment or the punditry, before the people have weighed in.

Moreover, Dean is a candidate who really does need some tempering through political competition. There are legitimate questions about his candidacy that need answering: Can he offer a positive vision for governing as well as a blistering critique of Bush? Can he persuade as well as energize? Is the excitement of his core supporters contagious to those swing voters that he has so often dismissed as irrelevant? Can the Dean campaign diversify, transcending its early origins as a sort of therapy group for upscale liberals? Will the candidate learn to take the cultural issues that many voters care passionately about more seriously? Can he become more self-disciplined in his off-the-cuff remarks, which are storing up treasure for Republicans in the fall? If the answers to these questions are negative, then it would be nice to know before Democrats entrust him with the tough challenge of trying to unseat George W. Bush.

And then there are the issues. Dean has rightly boasted of a fine centrist record as governor of Vermont, but his light-on-issues, heavy-on-anger presidential effort has borne little resemblance to that record.

He's flip-flopped on trade, adopting a Kucinich-Lite position that repudiates the Clinton legacy of trade expansion and a centuries-old Democratic tradition of support for open trade. Can he explain what he would do to make his "fair trade" rhetoric actually work for a stronger economy? He's the one candidate who's called for repeal of the No Child Left Behind education reform initiative, thrilling anti-testing zealots who don't seem to mind failing schools for poor and minority kids. What's his vision for education reform? In his fervor to define himself not by principle, but by maximum opposition to Bush, he's refused to countenance letting the middle class keep the tax cuts that accompanied the big bonanza for the wealthy. Does he have a plan for making taxes fairer and lower for hard-working middle-class families?

And most of all, Gov. Dean has risen to prominence by battening on hostility to the war in Iraq. Can he lay out a comprehensive, internationalist vision for foreign policy and national security that is tougher and smarter than Bush's?

All these questions, about each candidate's strategy, temperament, vision, and stance on the issues, need to be raised and answered before Democrats choose a nominee. Howard Dean is no exception. In his endorsement speech yesterday, Al Gore stressed the very high stakes facing Americans in the coming presidential election. That's precisely why this is no time for a coronation.