WASHINGTON — Aspiring first ladies, once demure figures on the sidelines of White House campaigns, have become the rapiers of the 2008 race, wading into political debate and attacking their husbands’ opponents.

In a campaign of unprecedented intensity — the leading American pollster Frank Luntz describes it as the most fascinating since 1896 — the wives of the presidential contenders are increasingly involved in political decisions.

Next year’s election also sees another new phenomenon, that of a potential “first gentleman,” who happens to be a former president. Having remained largely in the background, President Clinton appeared with his wife, Senator Clinton, at a rally in Des Moines, Iowa, last night.

The early fear of Clinton apparatchiks was that the former first lady could be eclipsed by her husband. But campaign teams have been surprised to find the female “other halves” presenting a similar problem.

In describing her husband, Senator Obama, as “the real deal,” Michelle Obama often seems a more energetic and determined presence than the candidate himself. Elizabeth Edwards, the cancer-stricken wife of John Edwards, has shown surer political instincts than the former North Carolina senator, who supported the Iraq war against her advice because veteran officials told him it was the safer stance to take.

In 2000, Cindy McCain was the archetype candidate’s wife, restricting herself to praising her husband’s character and discussing children’s issues.

This time, Mrs. McCain has stepped out of the shadows to lambast President Bush over the Iraq war in terms more strident than those normally used by her husband, Senator McCain, who is not known for mincing his words.

Of the spouses of the “big six” candidates, the lone traditionalists are Judith Giuliani, third wife of Mayor Giuliani, the Republican front-runner, and Ann Romney, who jokes all the other candidates on the Republican side have had more than one wife. She and her husband, Mitt, are Mormons. Despite the looming presence of Mr. Clinton, it has been the wives who have been making the biggest impact.

Mrs. Edwards is setting the pace as the model for the new type of “wannabe” first lady. Last week, she telephoned a live television show to assail Ann Coulter, the right-wing pundit who has proved to be her husband’s fiercest critic. She accused Ms. Coulter of having written a column that “suggested that my husband had a bumper sticker on the back of his car that said, ‘Ask me about my dead son,'” a reference to their son Wade who died in a car crash at 16. When Ms. Coulter responded that the column had been penned three years earlier, an impassioned Mrs. Edwards said, “I’m making this call as a mother, I’m the mother of that boy who died.” She went on to accuse Ms. Coulter of debasing politics with “hatefulness and ugliness.” The encounter resulted in a surge in donations to the Edwards campaign. Despite being diagnosed with inoperable cancer, Mrs. Edwards, 58, a lawyer who has children of nine and seven as well as a grown-up daughter, is a constant presence on the campaign trail.

Mrs. McCain, 53, who has a son in the Marines about to go to Iraq, voiced the concerns of many voters who support the war but believe it has been bungled. When asked what she thought of the Bush administration and Iraq, she replied, “I’m angry at them.”

Leading Republicans believe they have a star spouse waiting in the wings. Jeri Thompson, the wife of Fred Thompson, 65, who is due to announce his candidacy this month, is chief adviser to her husband. After one recent Thompson event, a senior Republican gazed admiringly as Mrs. Thompson, 40, a glamorous former Capitol Hill strategist, took to the wheel beside her husband in their BMW.

“Look, he’s got the trophy wife, and she’s in the driving seat too,” he said.