Senate campaign at a crossroads

Ever since she was the first to jump into the Democratic contest to succeed Edward M. Kennedy, Coakley has appeared to be on cruise control as her three opponents - US Representative Michael Capuano, businessman Stephen Pagliuca, and City Year co-founder Alan Khazei - have tried to gain traction through TV ads, a few attacks on Coakley’s record and positions, and grass-roots organizing.

The low-key campaign, often overshadowed in recent weeks by municipal elections, needs a dramatic churning before the Thanksgiving vacation week, analysts say, if any of the challengers hopes to become a viable alternative to Coakley, who has led in polls, fund-raising, and endorsements.

“If the dynamics of this race are ever going to change, it has to happen now,’’ said Mary Anne Marsh, a veteran Democratic strategist.

Because the primary is Dec. 8, the pace and structure of this campaign are unique, political veterans say. Not only is the special election for statewide office unusual, but, as opposed to typically long, drawn-out campaigns, it is an abbreviated contest broken up near the end by Thanksgiving, when voters’ interest might dim.

“People are not used to voting in December,’’ said Warren Tolman, the former Democratic state senator and 2002 gubernatorial candidate, adding that Massachusetts voters are conditioned to focus on elections coming right after Labor Day. “I have never heard of a post-Thanksgiving phenomenon.’’

Dan Payne, a Democratic media consultant with four decades of experience in state elections, called this campaign “a very strange bird.’’

“We don’t know who is going to come out to vote,’’ he said. “Only the insiders are going to know for sure when the election is happening and who they are going to vote for. This is going to be more like a party caucus than a primary.’’

Unlike with other statewide races, television and radio ads and direct mailings could have more influence. Some candidates are trying to quickly construct field operations, but the limited time between Kennedy’s death and the primary election makes it difficult to recruit workers and volunteers and build the sort of well-oiled organization that can deliver voters to polls in a huge numbers.

Though Khazei, in particular, is furiously trying to build such an organization, Coakley began with an organizational advantage because she had already run a statewide campaign, although against a very weak challenger. She also has a slew of endorsements from unions, a large number of state lawmakers, and EMILY’s List, the national women’s political group that is helping with organizational support and funds.

But Coakley is also putting a value on TV ads. Her media blitz began this past week with a 30-second spot featuring a woman whom Coakley helped when the woman’s health insurer denied coverage for breast cancer treatment. With female voters likely to make up a solid majority of primary voters, Coakley’s ad targets professional and suburban women, a significant part of her base.

The crucial question is whether Coakley can parry any attacks from opponents or media stories that challenge her record as a prosecutor and attorney general. If she holds steady in the polls or even increases her support over the next two weeks, there will be little that her three rivals can do to stop her, analysts say.

Her opponents understand that.

“The next two weeks will be critical, without question,’’ said Will Keyser, Pagliuca’s director of communications. “Either just one candidate can emerge as the likely challenger to Coakley, or two candidates or all three could all be growing together, which means the front-runner’s advantage would be shrinking.’’

Challenging Coakley in ads or on the stump poses risks, however. Such attacks, particularly by men on female candidates, can easily backfire.

“It is very dangerous,’’ Payne said. “It would really depend on how clever you are in fashioning the message. You need to soften the punch with humor and use of symbols that gently but effectively ridicule.’’

Capuano, a former Somerville mayor, will draw heavily on a big turnout from his Eighth Congressional District, home to many liberal activist voters, a bloc expected to have major influence on Dec. 8. He, too, has strong union endorsements, and he has picked up the backing of most of his Massachusetts congressional colleagues, but there is no guarantee they can provide significant ground support.

Capuano has stepped up his advertising, pushing hard his message that he is the only candidate who knows how to work the levers in Washington to deliver for Massachusetts. He also seems most willing to engage aggressively with Coakley. On Friday, he sharply criticized Coakley, who opposes capital punishment, for filing a Supreme Court brief that has angered opponents of capital punishment.

Capuano had initially registered as a distant second to Coakley in the polls. But Pagliuca, who is dipping into his $400 million fortune to pay for his first foray into politics, has raised his visibility from almost zero to running neck and neck with Capuano in some published surveys.

Pagliuca, a venture capitalist and co-owner of the Boston Celtics, has spent more than $3 million on ads since late September and is expected to spend at least $2 million more by primary day.

“He is squeezing Capuano in the polls, but the question is, do all his ads translate into getting people to the polls?’’ Marsh said.

Khazei has energized many volunteers and has sparked interest with a strong campaign message rooted in his experience in public service. But whether he can compete financially, and build enough of an organization in time, is another question.

Khazei’s campaign says it can. The candidate raised an impressive $1.1 million in his first few weeks, and aides said he equaled that amount in the last four weeks.

His campaign aired its first ad last week, and it promises to be competitive on the airwaves. “We know we will be outspent on TV,’’ said spokesman Dave Jacobson. “But we will have a strong buy.’’