Now that no clear Democratic front-runner has emerged from the Iowa caucuses and the New Hampshire primary, a campaign that had been all about momentum and money has become a furious race for the 2,025 delegates needed to clinch the nomination.
That gives newfound weight to the preferences of major Democratic Party leaders and elected officials, who can provide organizational help, fundraising aid and a network of supporters.
But the endorsements matter for another reason. Unlike past nominating contests, this one may be so close and protracted that the votes of "super delegates" could prove decisive.
Super delegates are House members, senators, party officials and other elected leaders who get to attend the Democratic presidential convention in August because of their positions and are free to vote their personal preferences. They are not bound by votes in their respective states.
So there are essentially two campaigns unfolding simultaneously: one for rank-and-file voters; the other for the 796 super delegates who account for nearly 40% of the total needed to win. Sen. Hillary Rodham Clinton of New York now leads with 163 super delegates, and Sen. Barack Obama of Illinois has 64, according to an Associated Press tally.
Erstwhile presidential candidate and New Mexico Gov. Bill Richardson looms as a trophy endorsement. The candidate who reels in Richardson gets a super delegate and a high-profile Latino who has the loyalty of New Mexico state lawmakers and donors -- all rolled into one.
The report last week that he was dropping out of the Democratic presidential race had barely moved on the wire services when Richardson's phone rang.
It was the Clintons, looking for his endorsement. Phone calls from Obama and former Sen. John Edwards of North Carolina came soon afterward.
"There's a massive push for endorsements," Richardson, who hasn't committed himself, said in an interview. "It's gone pretty far."
Sen. Claire McCaskill was another prize. The Missouri Democrat had been holding out, opting to stay neutral during the campaigning in Iowa and New Hampshire.
Her hesitation was in part a courtesy to Clinton. In the spring, she said, she had her first real face-to-face conversation with Clinton when the two met for lunch. Clinton knew that McCaskill leaned toward Obama but asked for a favor: Would she at least hold off and make no endorsement?
McCaskill agreed to wait.
But in recent weeks, Obama's campaign had been in touch, asking if she'd take a call from the candidate and hear his pitch.
McCaskill said there was no need. She considered Obama a friend and was grateful that he had campaigned for her in 2006, helping her get to the Senate. Plus, her children like him and had been nagging her to endorse. So on Sunday morning she made her announcement.
"It was really just now or never," McCaskill, also a super delegate, said in an interview. "If I wanted to try and make a difference, obviously it was do it now or stay on the sidelines until the nominee was decided."
The maneuvering for super delegates reflects a campaign that has taken unpredictable turns, forcing candidates to improvise on the fly.
Until recently, few believed the race might stretch past Feb. 5, when 24 states including California hold primaries and caucuses. Clinton said as much in December in a reception with donors in Sacramento.
But even after the bonanza of delegates is doled out on what is being called Super Duper Tuesday, the race could be up for grabs. That's because the winners of these contests do not automatically scoop up all of the delegates. Rather, in California, New York and elsewhere, delegates are awarded in proportional fashion. Clinton or Obama could finish a strong second and conceivably pick up enough delegates to deprive the other of the magic number needed to lock up the nomination.
So the contest could still be in limbo after Feb. 5, giving super delegates enhanced influence.
"There is the potential for this to be fairly evenly divided all the way to the end," said Chris Lehane, a spokesman for Al Gore's presidential bid in 2000 and a Clinton supporter.
Whether it will be a two- or three-person contest on the Democratic side is unclear. Edwards is mounting an intense campaign in South Carolina, where he was born. After a third-place finish in New Hampshire, he needs a strong result in South Carolina to remain competitive through the Feb. 5 vote.
In this uncertain environment, endorsements and super delegates are coveted.
Historically, endorsements have sometimes fallen flat. Former Vice President Al Gore endorsed Howard Dean's 2004 presidential campaign, but Dean, after placing third in the Iowa caucuses, made a loud, boisterous speech that his candidacy never overcame.
Yet validation from high elected officials can give a candidate access to their supporters and fundraisers -- or simply some much-needed help as surrogates on the trail.
California Lt. Gov. John Garamendi on Friday announced he was endorsing Clinton. He said he would quickly send out an e-mail to 300,000 of his supporters discussing the endorsement. His wife, Patti, served as a senior official in the Peace Corps during the Clinton administration, and will help as well.
"We are a sisterhood in many ways, and I've had the privilege of knowing her very personally," Patti Garamendi said.
Endorsements also carry symbolic value. Following a New Hampshire primary in which Clinton soaked up the female vote, Obama is eager to show alliances with high-profile women.
McCaskill said of her endorsement: "It may give some women permission to take a second look at Barack Obama."
A kind of mini-primary played out for the endorsement of the popular Arizona governor, Janet Napolitano.
Both Clinton campaign manager Patti Solis Doyle and former Iowa Gov. Tom Vilsack asked Napolitano to back Clinton, according to Barry Dill, a political advisor to Napolitano.
Obama met with the governor last February, and the two have been "talking ever since," Napolitano, a super delegate, said in an interview. With her endorsement comes "a number of volunteers and people" who have worked with her in previous campaigns, Napolitano said. "Many of them will support Obama."
For some female elected officials, endorsing Obama over Clinton can seem an act of betrayal. They want to see Clinton break the glass ceiling. California state Sen. Gloria Romero said she wore an Obama button on the floor of the Assembly last week and got a withering look from another female lawmaker.
"She came up to me and said, 'You've got to be kidding.' " Romero recalled. "She was shocked that I'd gone with Obama."