Just 18 days after Rep. Nancy Pelosi (D-Calif.) became the nation’s first female Speaker and the face of the Democratic Party, Sen. Hillary Rodham Clinton (D-N.Y.) announced that she was “in it to win it,” launching the most successful presidential campaign ever undertaken by a woman.

Now that that effort has fallen short, Pelosi will be the most powerful female politician for several years to come — and perhaps longer. She is the most powerful woman in American government, even if Clinton is better-known.

And while it is unlikely that the 68-year-old Speaker will eclipse Sam Rayburn’s record 17-year reign of the House, it is not unthinkable that Pelosi could match Tip O’Neill’s 10-year run.

Later this summer, Pelosi will release a book on female empowerment, Know Your Power: A Message to America’s Daughters. Shortly after that she will lead one of the most eagerly awaited Democratic conventions in recent memory.

“I hope she will take more visibility and I hope more women are seriously discussed for the vice presidency,” said Marie Wilson, president and founder of The White House Project, which is dedicated to advancing women into leadership in politics and other endeavors. Wilson said that the more women get involved in politics, the less unusual it will seem for a woman to be president or hold any other office.

Depending on what move Clinton makes next, Pelosi could resume her role as the female face of the Democratic Party even as Sen. Barack Obama (Ill.) becomes the party’s standard-bearer.

Before Clinton put “18 million cracks” in the glass ceiling that has kept women from the Oval Office, Pelosi talked of breaking through a “marble ceiling” to win the Speakership.

While she never played the “gender card,” Pelosi did emphasize diversity and her gender in her candidacy for leadership, said Marc Sandalow, who wrote a biography of Pelosi, Madam Speaker.

“It was useful in getting swing votes,” Sandalow said.

On the day she became Speaker, Pelosi emphasized her personal history not just as a woman, but also as a mother and grandmother, inviting a throng of children to take the House dais with her.

She subsequently turned to more universal issues, ending the Iraq war and enacting parts of the “Six for ’06” agenda. But every now and then at a press conference or other event, she breaks the chatter by yelling, “Do I have to use my mother-of-five voice?”

Clinton alternated on the campaign trail between playing up her gender and playing it down. Trailing heading into the New Hampshire primary, she teared up to answer a question and won the hearts of many voters. But then she turned to a get-tough message of experience with the “3 a.m. phone call” advertisement heading into the Texas primary.

Through it all, Pelosi remained the more powerful woman in terms of raw authority. Pelosi commands a chamber of Congress, while Clinton is a junior senator from New York. Yet Clinton was for a time the presumed nominee, who would have controlled the party machinery heading into the November election, and could well have been president.

Pelosi’s role as leading woman of national politics depends, experts say, on whether either nominee picks a woman to join him on the ticket, including Clinton herself.

Republicans put in place an eight-year term limit on Speakers, along with six-year limits for chairmen, when they took over Congress in 1995. Newt Gingrich (Ga.) was ousted before he had the chance to test it. But the rule was rescinded in 2003 to give then-Speaker Dennis Hastert (Ill.) the opportunity to stay past the eight-year limit. In 2006, he became the longest-serving GOP House Speaker.

Following the 2006 elections, Democratic committee chairmen were shocked to realize that they had passed a set of rules that set term limits on committee chairmanships. Less remarked upon was that the same rules left out term limits for the Speaker.

“When the issue of term limits has come up in the Democratic Caucus, it has been overwhelmingly defeated,” said Oversight and Government Reform panel Chairman Henry Waxman (D-Calif.).

Waxman said he is confident the rule will be changed when Democrats re-do their rules package next year.

“Speaker Pelosi has said she would support eliminating them in the next term. It’ll come up,” Waxman said.

But other committee chairmen said they knew of no such assurances.