On a hot Saturday in June 2002, Fred Thompson married his second wife, Jeri Kehn, in an unventilated Congregational church in her home town of Naperville, Ill. Ms. Kehn, in a Valentino gown, was a 35-year-old press consultant for a Washington law firm; Mr. Thompson, a 59-year-old senator from Tennessee.

“I think he will be a calming influence, and she will be good for him,” Ms. Kehn’s mother, Vicki Keller, said at the time.

It was a triumphal return for Ms. Kehn, who had left Naperville for college and spent much of her 20s biding her time in Nashville, Tenn., without a clear career path, living with a boyfriend whose main claim to fame was getting arrested in Red Square for unfurling a pizza parlor banner in the last days of the Cold War. Ms. Kehn left three court judgments behind her in Nashville, one of which remains unpaid today, and a court twice garnished her wages.

But after meeting Fred Thompson, Ms. Kehn began establishing herself in Washington Republican circles, and marriage more than consolidated her place in the city. Today, Jeri Thompson, 40, has emerged as a driving and at times divisive force within the presidential campaign her husband is preparing to launch, one that could make her the nation’s youngest first lady since Jacqueline Kennedy.

In the nascent Thompson campaign — anticipated with high hopes by many conservatives unsatisfied with the current crop of GOP candidates — Jeri Thompson plays a role arguably as influential as those of two better-known spouses of Democratic candidates, President Clinton and Elizabeth Edwards. She helps shape her husband’s conservative message and image, has been a strong voice urging him to run, and recently helped instigate a shake-up that pushed aside Mr. Thompson’s first campaign manager and his research director.

“They’ve been a team since they got married,” said Victoria Toensing, a prominent Republican lawyer who got her start in Washington working for Fred Thompson three decades ago and is now friends with his wife. “Husbands and wives can be teams nowadays in politics. There are no more Bess Trumans staying home in Missouri.”

It has been a remarkably swift climb to prominence, and one that gave Jeri Thompson little familiarity with the public spotlight. She married Fred Thompson shortly before he retired from the Senate to focus on his career as an actor and has stayed home raising their two young children.

The current GOP presidential field provides two examples of the political perils of a controversial spouse. In 1999, in the midst of Senator McCain’s first presidential campaign, his wife, Cindy, addressed her previous addiction to painkillers, which eventually led her to steal drugs from her nonprofit medical group. Mayor Giuliani’s third wife, Judith, has endured stories about her previous marriages and her penchant for expensive shopping.

Even before her husband’s campaign is official, Jeri Thompson has had her share of publicity. She has had to fend off insinuations about her age and good looks — including a New York Times reference to her as a “trophy wife.” And some advisers inside the Thompson campaign have anonymously criticized the strong hand she has taken in running it.

Campaign sources described Jeri Thompson as firm, straightforward, and assured of what she wants to do, but unfamiliar with the nuts and bolts of campaigning. Many decisions have been held up awaiting her approval, they say, from routine matters such as travel schedules and car manifests to weightier ones including direct-mail efforts, personnel choices, and the timing of the campaign kickoff.

One person directly familiar with the campaign said Mr. Thompson was the architect of the strategy to portray her husband as the true conservative in the race. The source said Mr. Thompson works mostly from the couple’s home in McLean, Va., “running the campaign from the kitchen table.” She frequently calls aides and demands answers quickly. “Everything for her is at Defcon,” the source said, speaking on the condition of anonymity because the person was not authorized to speak on behalf of the campaign.

Neither Jeri Thompson nor the Thompson campaign would comment for this story.

Growing up in Naperville, 30 miles west of Chicago, Jeri Kehn was a member of her high school’s state-champion spirit squad, the Starlettes, known for their white boots and matching Stetsons. She majored in English at DePauw University in Greencastle, Ind., where she met the man with whom she would spend much of the next decade: Bernard “Chip” Alvey of Owensboro, Ky.

Mr. Alvey experienced a brief flash of international notoriety while in college — he was one of four DePauw students who, on a visit to Moscow in 1985, were detained after taking a photo of a sign they unfurled in Red Square advertising a favorite pizzeria back in Greencastle.

Ms. Kehn and Mr. Alvey dated after college and eventually lived together in a house he bought in Nashville. Mr. Alvey said in an interview that he was working as a stockbroker and helping to support Ms. Kehn, who, he said, held a variety of jobs but nothing “career-oriented.”

Money was a problem for the couple. In 1994, Ms. Kehn was ordered to pay $10,000 in unspecified civil damages related to a 1990 car accident in Naperville in which she swerved across three lanes on a highway and struck another car, totaling it. The outstanding balance was paid off in 1999. In 1996, the Davidson County court in Nashville ordered a $900 judgment against Ms. Kehn in a case brought by an anesthesiologist, and garnished her wages at a communications company. In 1997, the court ordered a $1,700 judgment against Ms. Kehn for unpaid medical bills at Nashville’s Baptist Hospital and again ordered her pay garnished. But Ms. Kehn had left for another job, and the debt is still listed in court records as unpaid.

Mr. Alvey has suffered larger-scale financial woes. At one point in the late 1990s, he owed $93,000 to a builder, and in 2005, the Internal Revenue Service won a $270,000 judgment against him. The couple never married, Mr. Alvey said, though the court documents involving both of Ms. Kehn’s medical debts give her name as Jeri Kehn-Alvey. Mr. Alvey, who now lives in Louisville, Ky., couldn’t recall just when he and Ms. Kehn broke up but said it was probably before she started dating Mr. Thompson. He said they haven’t spoken in four or five years.

It was at a Nashville Fourth of July party in 1996 that Ms. Kehn met Mr. Thompson, a former staff member of the Senate Watergate committee, who built a successful career as a lawyer, lobbyist and Hollywood actor before winning his Senate seat in 1994. They began dating sometime in the next year, according to Roger Schneider, an Internet entrepreneur who was working with Ms. Kehn at the time on a venture to create a Web site focusing on Tennessee politics.

At some point during their work together, Mr. Schneider recalled in an interview last week, Ms. Kehn mentioned that she was seeing Mr. Thompson: “She said, ‘I’ll be speaking to Senator Thompson this weekend,’ and I said, ‘Oh, really?’ She said, ‘Yes, we date occasionally.’ “

Mr. Schneider said he suggested that they approach Mr. Thompson’s office with a proposal to create a Web site for him separate from his official Senate one. Mr. Schneider, a Democrat, said he was aware he might be putting Ms. Kehn in an awkward spot by having her pitch the idea to Mr. Thompson, but he said she seemed enthusiastic about trying. “She was comfortable with the proposal,” said Mr. Schneider, who now runs a technology firm in Huntsville, Ala. “She was a big girl and knew what was going on.”

On August 5, 1997, Ms. Kehn sent M r . Thompson’s Senate office a 12-page proposal to “design, develop, host, andmaintain a world-class multimedia Web site” at a cost of $45,000 a year. As her qualification for the contract, Ms. Kehn cited her job at a small Nashville firm that provided daily news summaries to health-care companies.

Two weeks later, Mr. Thompson’s staff sharply rejected the proposal, according to memos located by the Memphis Commercial Appeal in the Thompson Senate archives, stored at the University of Tennessee. “I consider this project technically vague and stunningly overpriced,” a staff member wrote.

In the end, Mr. Schneider said, he and Ms. Kehn wound up hosting a single Web chat between Mr. Thompson and constituents, at a cost of about $4,000.

But Ms. Kehn would soon have more success breaking into Washington. In 1998, she was hired at the Republican National Committee by Clifford May, then the head of the public affairs office, who said she came recommended to him by Mitch Bainwol, then the RNC’s chief of staff and later chief of staff to Mr. Thompson’s fellow Tennessee GOP senator, Bill Frist. “She didn’t have a lot of political or media experience, but struck me as a really bright and energetic person I was willing to take a chance on,” Mr. May said.

How much Ms. Kehn’s ties to Mr. Thompson helped her in Washington is hard to gauge. Mr. May said it was no secret that Ms. Kehn was dating Mr. Thompson, who divorced his first wife in 1985 and developed a reputation as a ladies’ man linked to, among others, country singer Lorrie Morgan and cosmetics executive and GOP fund-raiser Georgette Mosbacher. “A smart, good-looking woman in Washington in her 30s dating a member of Congress doesn’t come as a shocker,” Mr. May said.

Ms. Kehn, he said, was adept at arranging for Republican figures to appear on cable news shows. “She had a good sense of where the news was going, the differences among the various shows,” Mr. May said.

Despite the unglamorous nature of her first job in Washington, Jeri Thompson’s supporters today describe her as a powerful political operative. Whether that label fits her roughly five years of full-time work here is hard to determine, given the relatively low profile she kept at her various jobs. An exception was a 1999 appearance on “The O’Reilly Factor” to criticize a skit that President Clinton did the night before at the White House Correspondents’ Association dinner. “I’m certain that I’m not the only American that was incredibly appalled at the fact that Bill Clinton is more credible as a clown than he is as a president,” she told Bill O’Reilly.

From the RNC, Ms. Kehn moved to the Senate Republican Conference, and from there to the public relations and lobbying firm Burson-Marsteller, where she worked full time between February 2001 and January 2002.

According to two people who have worked for Burson-Marsteller, one currently and another formerly, Ms. Kehn got the job at the behest of Kenneth Rietz, the head of the firm’s Washington office at the time, as a favor to Mr. Rietz’s friend Fred Thompson. (Mr. Rietz, now retired from the firm, is a Thompson campaign adviser.)

But Charlie Black, chairman of BKSH & Associates, a lobbying subsidiary of Burson parent WPP Group, disagrees. “We had to recruit hard to get her to come to Burson,” said Mr. Black, an adviser to Mr. McCain’s campaign.

By the time Ms. Kehn and Mr. Thompson married in June 2002, she had moved to a political consulting job at Verner, Lipfert, Bernhard, McPherson and Hand, a law firm whose partners included former senator Bob Dole, a Republican of Kansas. But she left that job and has generally been less visible on the D.C. social and political scene while raising her children — until her emergence in recent months at the center of the campaign.

Back in Huntsville, Mr. Schneider said that, even as a Democrat, he is enjoying the sight of his onetime business partner in a leading role.

“She’s a very bright lady, and she can be a dynamo,” he said.