Some who have been through the pain of a floundering run say hanging in there makes perfect sense.
Michael Meehan, who was an adviser to the 2004 Kerry campaign, recalls the talking heads on the Sunday shows didn't even bother to mention his candidate in their predictions for Iowa a week before the caucus.
Kerry won Iowa. And eventually, the nomination.
"Even if you finish second in Iowa but had no money in the bank, with today's fundraising tools, you could make 20 million bucks in one day," Meehan said. "That is enough to put gas in the plane to get you to New Hampshire. It is lighting in the bottle but it is totally doable."
Of course, only one candidate, at most, can be the surprise of the year. And Murphy takes a dimmer view of this year's crop.
He recalled a 2 a.m. meeting with a flailing McCain late in 2007. The bar had already closed for the night, leaving the two of them to drag chairs over from another room. McCain was mulling dropping out. Murphy, who was backing another candidate, said he advised the senator to hang in there. McCain was getting no traction in Iowa, but his popularity in New Hampshire, where he had been all the rage in 2000, could still be his ace, Murphy said.
"I told him, 'Why on earth would you drop out when you haven't played that card?'"
McCain focused exclusively on the Granite State, and his win there propelled him to the 2008 nomination.
But Murphy questions whether some candidates in the current race have any card to play. Stubbornness, he warns, can come at a cost.
"If you start to look like a loser on the national stage, it takes a toll back home," Murphy said. Former Texas Rep. Beto O'Rourke's remarkable plunge in popularity on the national stage, for example, could threaten his future viability as a statewide candidate.