The only presidential spouse to win election to the Senate, Clinton is regarded as the early front-runner. But her celebrity, her lead in the polls and the formidable organization she built with her husband aren't frightening others away. Up to a dozen Democrats are either running or preparing to enter a contest that appears more competitive now than it did a few months ago.
"I'm in. And I'm in to win," Clinton declared in a written statement on her campaign Web site. "We will make history and remake our future."
She also appeared in a Web video, Oprah-style, in a venue designed to soften her image as a remote and cautious politician. One-upping a rival, Sen. Barack Obama, who made his announcement online as well, Clinton said she would employ Internet technology to interact with voters in a series of video chats this week.
"This is a big election with some very big questions," Clinton said in her statement. "How do we bring the war in Iraq to the right end? How can we make sure every American has access to adequate health care? How will we ensure our children inherit a clean environment and energy independence? How can we reduce the deficits that threaten Social Security and Medicare?"
The 59-year-old New York senator, who once wrote a book about raising children entitled It Takes A Village, said she wanted her campaign to be a "national conversation."
"So, let's talk. Let's chat. Let's start a dialogue about your ideas and mine, because the conversation in Washington has been just a little one-sided lately, don't you think?" Clinton said in the nearly two-minute video that shows her seated casually on a couch in her Washington residence.
"I have a feeling it's going to be very interesting," she added, teasingly.
Her decision to run had been expected by the end of this month, but the exact timing came as a surprise. Clinton's campaign denied that Obama's decision to join the race had forced her hand, though the videotaping of her announcement took place after the Illinois senator revealed his plans.
Clinton's ability to attract national attention has never been in question, and aides said they expected the media coverage surrounding her decision to extend through President Bush's State of the Union speech on Tuesday.
Her announcement largely overshadowed the entry of two other presidential candidates this weekend, Republican Sen. Sam Brownback of Kansas and Democratic Gov. Bill Richardson of New Mexico. Richardson, who is Hispanic, assures that Democrats will have three candidates trying to make history: the first woman, the first African-American and the first Latino seeking to become president in the same year.
In her announcement, the senator made no mention of her husband, former President Bill Clinton. In her video, a collection of family photographs on a table in the background was his only (barely) visible presence as she began her run.
However, she repeated a trademark line from his campaigns, that Americans who "work hard and play by the rules" deserve to reap the benefits of the American dream.
And former Democratic Party chairman Terry McAuliffe, a key Clinton fundraiser and adviser, said the former president will be "very active" in the campaign.
"He wants to make sure that his wife is elected," McAuliffe said on CNN. "The two of them will be out there campaigning extensively."
Mrs. Clinton's popularity rose after the disclosure of her husband's affair with a young White House intern, Monica Lewinsky, and his subsequent impeachment by the House. (The Senate did not convict him.) Since the former president left office, his standing in the polls has risen, and Democratic activists often say they wish he could have run for a third term.
Mrs. Clinton plans to highlight her experiences as first lady and in the Senate, arguing that her "lifetime record of results" make her more qualified than her major rivals to assume the presidency.
Only a new president can "undo Bush's mistakes," she said yesterday, and "restore our hope and optimism," "renew the promise of America," and "regain America's position as a respected leader in the world."
One of her challenges, Democrats say, will be to capitalize on nostalgia for the Clinton years, while at the same time convincing voters that she is a forward-looking candidate. Her rivals will try to turn the Bill Clinton era against her, by suggesting that 20 years of Bushes and Clintons in the White House are enough and that it's time for the country to move on.
On Iraq, an issue that could pose difficulties for her in the primaries because of her early support for the invasion, Clinton has stepped up her criticism of Bush's policy in recent weeks, calling it a "failed strategy" and proposing a cap on the number of U.S. troops there.
She has not demanded an immediate withdrawal of U.S. troops, however, which, polls show, many Democratic voters want. One of her main rivals, 2004 vice-presidential nominee John Edwards, is demanding an immediate pullout of 40,000 to 50,000 U.S. soldiers.
A new national poll, released yesterday, showed Clinton with a wide lead in a matchup against 12 other Democrats. Clinton was at 41 percent, with Obama at 17 percent and Edwards next at 11 percent.
Former Vice President Al Gore, who has said he has no plans to be a candidate, and 2004 nominee John Kerry, who is considering a run, were the only other Democrats to receive more than 3 percent, according to the ABC News/Washington Post survey.
Other opinion surveys show her as the most polarizing candidate in the field. Many Democrats are skeptical about her chances in a general election, with polls showing that more than 40 percent of Americans say they will never vote for her for president.
Clinton, who faced similar doubts about her electability when she launched her Senate try in July 1999, boasted yesterday of her two "landslide wins" in New York. She said she knows "how Washington Republicans think, how they operate and how to beat them."
As she kicked off a candidacy that is expected to be the most serious run for the White House by a female candidate, Clinton stressed women's issues, including her work in the Senate to force the Bush administration to allow the sale of the Plan B contraceptive without a prescription and her visit to China as first lady to push for women's rights.
She also spoke of the need to provide "quality, affordable health care for every American." Clinton's effort to spearhead a universal health care plan collapsed in 1994, but the issue once again tops the national agenda, and no other major candidate can match her expertise in that area.
In a statement, Obama, who some analysts regard as her strongest challenger, described Clinton as "a good friend and a colleague whom I greatly respect. I welcome her and all the candidates, not as competitors, but as allies in the work of getting our country back on track."
That comment was different in tone from Clinton's stiff response when a TV interviewer pressed her on whether she thought Obama was qualified to be president.
"I'm going to let all of those decisions be sorted out by voters," she replied.
Clinton plans a campaign swing next weekend to Iowa, where the first delegates will be chosen less than a year from now. Her last visit to the state was in 2003, and polls there show her trailing Edwards, who nearly won the caucuses in 2004 and has worked hard to maintain his organization in the state.
Some have suggested that her celebrity could be a disadvantage in Iowa, which prizes one-on-one contact with would-be presidents.
"She's brilliant. She's eloquent. She drips charisma. She's the former first lady of the United States, all of which lends her rock-star status. But it's a double-edged sword," said Gordon Fischer, a former Iowa Democratic chairman who is backing former Iowa Gov. Tom Vilsack's presidential bid. "I wonder if, practically, it's going to be difficult for her to visit coffee houses and church basements and union halls with the media entourage."
Clinton spokesman Howard Wolfson said she is "committed to doing this the old-fashioned way," including visits to living rooms in Iowa, where party activists have had little or no contact with Clinton.
The exploratory committee that she announced yesterday will allow her to begin collecting and spending money for a presidential campaign. Her fundraising prowess isn't in doubt, and she is expected to be the best-funded contender in the Democratic field, with estimates of the amount she will raise this year ranging as high as $100 million.
According to the most recent Federal Election Commission report, Clinton had more than $14 million in the bank after her successful 2006 re-election effort, money that can be used for her presidential run. She spent about $26 million in her 2006 campaign, against minimal opposition, prompting questions about the financial discipline of her campaign team. Her advisers said much of that money had been spent to broaden her fundraising base in advance of a presidential try.