With polls showing the two main candidates running neck and neck ahead of voting tomorrow, President Barack Obama has left Washington to plunge headlong into the suddenly tumultuous race in Massachusetts for the US Senate seat left open by the death of Edward Kennedy.
Something close to panic has gripped Democrats nationally since it became clear that what should have been a cake-walk for their candidate, Massachusetts Attorney General Martha Coakley, had become anything but with an unexpected late surge by her Republican foe, State Senator Scott Brown.
Such is the concern that the White House announced only on Friday afternoon that Mr Obama would abandon his Sunday plans -- though not an early visit to church to pray for Haiti.
Instead he is prepared to risk his own prestige by appearing alongside Ms Coakley at a rally at Northeastern University in Boston.
Speaking to 1,500 supporters gathered in a basketball arena, the President made little mention of his healthcare policy that is generating considerable opposition in Massachusetts, and instead attacked Mr Brown for not supporting the bank bail-out tax.
"We asked Martha's opponent, what's he going to do, and he decided to park his truck on Wall Street," Mr Obama said. "Let me be clear: Bankers don't need another vote in the United States Senate. They've got plenty."
It may not be too late. "In the past 24 hours, the lights have come on," Ellen Malcolm, the founder of Emily's List, which supports women candidates who back abortion rights, said while campaigning with Ms Coakley at the weekend. "Democrats have woken up.''
Since Friday, she has also been joined on the trail by other party stars, including former President Bill Clinton and the state's senior Senator, John Kerry.
Barring any recounts, the outcome of the race should become clear by late tomorrow or early on Wednesday morning -- the first anniversary of Mr Obama's inauguration.
If it turns out that Ms Coakley has lost, the consequences for the President could be devastating -- not least because it would deprive the Democrats of their 60-strong super-majority in the Senate which protects against Republican filibustering.
The Republicans, who themselves never imagined that a seat which has belonged to Democrats for more than half a century would ever seriously be in play, hardly dare hope for a win.
Defeating Ms Coakley and welcoming Mr Brown to Washington would give them the opportunity potentially to cripple the healthcare reform bill at the very moment it was due finally to emerge from Congress.
The move would also seriously hurt Mr Obama's other domestic priorities, for example on climate change and immigration.
Tomorrow's vote is a "referendum on the national healthcare bill," Mitch McConnell, who leads the Republicans in the US Senate, contended yesterday.
"They have arrogantly ignored American public opinion all the way to this point."
He added: "Regardless of the outcome on Tuesday we know that in the most liberal state in America, you're going to have a close election to the United States Senate."
Mr Brown is a telegenic candidate with populist appeal who criss-crossed the state in a pick-up truck until this weekend he decided it was time he graduated to a bus.
His campaign has become something of an insurgency in what is a Democrat stronghold, fuelled by the wildly enthusiastic backing of conservatives from all across the country, including the Tea Party Republicans who have rushed in volunteers and raised funds.
"Come Tuesday we are going to send a thunderclap around the country -- to let people know, not only here in Massachusetts but [also] the people in Washington that they're tired and we're tired of business as usual in Washington," he declared at a weekend rally.
"We feel there's no debate, out of control taxation, out of control spending and we can do better."
While registered Republicans are heavily outnumbered in Massachusetts, they clearly have enthusiasm and fervour on their side.