Lopsided turnout in favor of Democrats at the Iowa caucuses, a huge fund-raising advantage for the Democratic presidential campaigns, and an atmosphere of dissatisfaction among the Republican base are prompting warnings that any Republican presidential nominee could struggle to win in November.

“There is an enormous degree of Democratic enthusiasm. There’s a great deal of Republican angst,” a prominent political analyst, Norman Ornstein of the American Enterprise Institute, said.

“You have to give the edge to the Democrat, without question,” a Democratic strategist, Hank Sheinkopf, said.

In Iowa last week, about 221,000 people turned out for the Democratic caucuses, despite the fact that those sessions tend to be more lengthy and involved than the Republican ones. On the Republican side, about 116,000 Iowans voted. That figure was up more than 30% from the last contested primary in 2000, but nowhere close to the Democratic number.

In New Hampshire’s vote today, Democratic voters, buoyed by independents picking up ballots in that primary, are expected to outnumber Republicans again.

Nationally, Democratic presidential hopefuls had raised $241 million as of September, while the Republican hopefuls pulled in just $175 million, according to figures filed with the Federal Election Commission. That $66 million advantage for Democrats likely grew further in the fourth quarter of 2007.

For most of the year, analysts have attributed the Democratic advantage to concern about the war in Iraq. However, as reports from Iraq have improved in recent months, Democrats seem to have maintained their energy as the candidates transitioned to talk about the economy other issues.

“The enthusiasm, the differential turnout, the differences seen in the money, the differences seen in the attraction of independents — it’s all a clear sign, in effect, that if the Democrats can’t win this, they had better find a different line of work,” Mr. Ornstein said.

However, he warned that huge advantages have often been frittered away, or disappeared, such as when Michael Dukakis held a 17-point lead in opinion polls in 1988 and lost the race to President George H.W. Bush. “Things could change dramatically,” Mr. Ornstein said. Among the few signs of life for Republicans at the moment are good fund-raising by the national party and growing voter dissatisfaction with the Democratic-led Congress.

Senator Obama’s impressive victory in the Democratic caucuses in Iowa last week is now having an impact on the Republican race, as those candidates scramble to embrace the mantra of “change” that defined the Illinois senator’s campaign and drove young voters to turn out. The Republican front-runner in New Hampshire and some national polls, Senator McCain, is viewed as a maverick in Washington, but one of his rivals, Mitt Romney, argued yesterday that Mr. McCain’s 21-year tenure in the Senate makes him ill-suited to compete with Mr. Obama.

“Why is there such enthusiasm about Barack? It’s in part because he’s not one of the insiders. He ran against three senators, at least in that last election. … He beat them all,” Mr. Romney said in a speech to the Nashua, N.H., Rotary Club. “Barack Obama may well become the Democratic nominee, and if we put up a long-term serving senator, who can talk about his years and years of experience, Barack Obama will do to him what he did to the other Democrats who had made the same pitch.”

Mr. Romney made no direct reference to Mr. McCain’s age, but any reference to his lengthy service reminds voters that he will be 72 if he takes office in 2009. Mr. Obama will be 47.

“Those 20-something and 30-something voters, they’re tired of the Baby Boomers. They want their parents to disappear,” a Democratic strategist, Hank Sheinkopf, said. “You’re going to have to work very hard to convince them that John McCain can meet those desires.”

To address that concern, Mr. McCain’s general election campaign would likely emphasize his bipartisan work on issues that resonate with young voters, such as climate change and, perhaps, immigration. “You can’t argue he hasn’t been an agent of change,” a Republican strategist friendly with the Arizona senator, Scott Reed, said. “He’s taken on a lot of Republican causes.”

Mr. Reed said Mr. McCain’s age has not been and would not be a major issue, unless the Arizona senator falls ill and sets off a round of stories about his health. “He’s got to be carXeful he doesn’t catch a cold,” the strategist said.

Mr. Obama would likely have the upper hand until he made a serious mistake, analysts said. A terrorist attack or major foreign policy crisis could also tip things to Mr. McCain by highlighting his experience.

“I don’t think you’d see a knife fight like you would with the other Republicans,” Mr. Reed said. “I think an Obama-McCain race would tend to raise the level of politics a few notches.”