They're worried. They should be.
Thousands upon thousands of the Democratic faithful and media hangers-on have flooded into Denver, a city whose downtown is now defined by traffic barriers, helicopters hovering, army trucks rumbling and men - almost all men - in every kind of uniform whose sole function is to tell you: "You can't go there."
The Democratic National Convention should be a celebration of a party on the cusp of routing the Republicans in Congress and recapturing the White House.
Instead, their candidate is essentially tied in the polls with a septuagenarian war hawk who knows little about economics and nothing at all about the Internet, even though Democrats traditionally enjoy a big lead during the summer.
Suddenly, Barack Obama seems vulnerable, his soaring rhetoric last season's movie. The fairytale campaign that galvanized the Democratic base is not playing so well outside it.
Women always prefer Democrats, except this time. Right now, Mr. Obama and John McCain are essentially splitting the women's vote. In the 2006 midterm elections, independents surged over to the Democrats. Now they seem to be ebbing back to the Republicans.
His campaign becalmed, Mr. Obama chose Joe Biden, as grizzled a warhorse as ever sat in the Senate, as his running mate. It was a safe choice. It had to be. Suddenly, Mr. Obama can't afford to take chances.
Now he has four days of exclusive media attention, at a national convention dedicated to the sole purpose of making the presidential nominee appear presidential.
Mr. Obama must use this opportunity to relaunch his campaign so convincingly that he eclipses next week's Republican sequel. The summer was won by John McCain. But in this game, autumn is the only season that counts. It's time Mr. Obama started to deliver.
Think about it: The United States is in the sixth year of an unpopular war; the government is mired in deficit and debt; people across the nation are watching their home equity evaporate; fuel costs have soared. The people rightly blame the Republican administration for all of it.
Surveying such a promising landscape, the Democrats dared to dream. They could discard the safe picks. Yes, Hillary Clinton had a perfect résumé and would have been the first woman presidential nominee. But refried Clinton? Was there nothing else?
They shrugged equally at the other veterans: Bill Richardson, the New Mexico governor who served in Bill Clinton's cabinet; Mr. Biden himself, with decades of experience in foreign policy; Chris Dodd, a senator with his own distinguished record; John Edwards, the handsome champion of the working man and woman. (We didn't know, then, about the affair.)
Instead, led by a zealous army of African Americans, the young and the urban affluent, they chose a charismatic former law professor and community activist whose oratory could curl your toes, and who just happened to be black.
But industrial workers, mothers struggling to hold the household together, owners of SUVs and minivans and pickup trucks often don't have a lot of respect for the opinions of the young, and even less for the condescending white-wine set. And some of them don't want to see a black man in the White House.
That is why Mr. Obama's faux pas on Saturday was so telling. In their first public appearance together, Mr. Obama introduced Mr. Biden as "the next president -" then he corrected himself, "the next vice-president of the United States."
And that's the point. In terms of experience and qualifications, a Biden-Obama ticket would have made more sense. We caught a glimpse of what might have been, Saturday, when the Delaware senator and chairman of the Senate Foreign Relations Committee - itself one of the most powerful jobs in Washington - his white hair tousled, holding down his wind-blown pages of text, growled and barked and stormed through a speech that warned against the "Bush-McCain" foreign policy that has "shredded our alliances and sacrificed our moral standing around the world."
