A former chief strategist for Howard Dean, whose 2004 presidential hopes plummeted from rock star status to also-ran,? predicts a similar fate for the Democratic darling of the ?moment, Vermont U.S. Sen. ?Bernie Sanders.

“There’s a big difference ?between 10,000 at a rally and turning out 3,500 caucus ?attenders on a cold winter night in Iowa. I suspect Bernie Sanders will learn the difference in February,” said Steve McMahon, Dean’s one-time top strategist. “His crowds are enthusiastic and large and fun to watch, but the question is whether they will be effective in the long run.”

Large crowds don’t necessarily translate into delegate support, McMahon said.

“Bernie Sanders needs to move the crowds into action and organize grass-roots support in the early states and so far, I haven’t seen any evidence that that’s occurring,” he said. “He doesn’t seem to be running a grass-roots campaign. It’s a campaign based on big crowds.”

The Summer of Sanders has seen the self-described socialist surge from nearly 50 points ?behind the Democratic front-runner, former Secretary of State Hillary Clinton, to within 15 points, ?according to Real Clear Politics’ average of polls.

Sanders’ aides had to scramble to find a new venue to accommodate more than 7,500 screaming supporters Monday as a planned town hall morphed into a roaring rally in Portland, Maine.

Sanders also recently played to 10,000 fans in Madison, Wis.

“He is drawing massive crowds in all sorts of places,” said Sean Trende, senior elections analyst at Real Clear Politics. “In an Internet age, there’s a segment that increasingly values authenticity. You saw that with Ron Paul. I think Sanders taps into that.”

Sanders has earned the backing of U.S. Sen. Elizabeth Warren’s anti-Wall Street wing of the Democratic party — mostly young, white progressives — but faces a challenge courting black voters, who have supported Clinton in the past, Trende said.

The 73-year-old Sanders does well in neighboring New Hampshire as a folk hero firebrand, but he likely will run out of steam, said Peter Hoe Burling, a former New Hampshire delegate for ?the Democratic National Committee.

“People talk about Howard Dean’s yowl, but the fact of the matter is, that campaign had peaked at a certain point,” Burling said. “It went as far as it was going to go and there’s the chance Bernie’s campaign is ?going to peak as well. In my mind, his campaign will peak at some point prior to the New Hampshire primary.”

Sanders can’t win in big states with deep reserves of delegates such as New York and California, said Matt Bennett, a veteran Democratic campaign strategist and Clinton supporter.

“He may do well in Iowa and New Hampshire, but he runs into a brick wall after that,” Bennett said.

“He’s not going to have the money or organization to challenge Secretary Clinton in multiple states at the same time on Super Tuesday,” Bennett said.

Sanders also could face high hurdles in the south, said Chip Felkel, a South Carolina-based Republican strategist not aligned with a presidential campaign.

“He’s been very impressive with what he’s been able to do crowd-wise and enthusiasm-wise,” he said. “I think that would carry over some in South Carolina, but he might be just plain too liberal for some of the Democrats around here.

“We’re just generally, even by national standards, more conservative in this state,” Felkel said.

“If he comes to South Carolina and has an impressive crowd, we’ll have to rethink that equation, but right now, I just don’t see it,” he said.