But it has been caught off guard by a submarine named Barack Obama, running silent, running deep — until he surfaced with a spectacular showing in the first round of fund-raising numbers. What startled Clinton's team was not just Obama's totals or his success at drumming up contributions over the Internet, but also how much he is collecting from the big donors who have fueled Clinton enterprises for the past decade and a half. "It was a real wake-up call," says a Clinton strategist.

Clinton's campaign still professes publicly to be unperturbed, maintaining that it never believed the race would be a cakewalk. "The game plan that we began this campaign with is the game plan we are using today," insists spokesman Phil Singer. But Clinton's advisers privately acknowledge that she is retooling her strategy on four fronts: intensifying her fund-raising, emphasizing her experience and policy depth (she's counting on the upcoming debates to put those on display), pondering when and how to go on the offensive against Obama and dusting off the "two for the price of one" theme of her husband's 1992 campaign. But this time it's Bill you would get in the bargain.

The fund-raising comes first. As her campaign chairman, Terry McAuliffe, discovered, Obama "works the phones like a dog. He probably did three to four times the number of events she did" in the first quarter. "No matter who I call," McAuliffe says, "he has already called them three or four times." So Clinton is stepping up the pace of her cash raising. Instead of big galas, she will be doing more fund-raisers in smaller settings that offer extra attention from the candidate — especially for those contributors who can pony up the maximum $4,600 total allowed by law for the primary and general elections. Whereas her forces once warned donors that it would be seen as an act of disloyalty to contribute to anyone but Clinton, they are now inviting Obama's fund-raisers to consider hedging their bets by helping her too. And they are reassuring a new and younger generation of fund-raisers that despite the size of her operation, there will be plenty of room at the table for them and their ideas.

Also being added are "small dollar" events, like a recent $100-a-head "Party on the Pier" at New York City's Pier 94, which are useful for collecting not only money but also e-mail addresses with which she might blunt the advantage that Obama has on the Internet. Having raised her money largely on the coasts until now, Clinton is going inland. Invitations just went out for a May 7 fund-raiser in Chicago, which is her hometown — and Obama's political turf.

Attending all those events across the country, however, means Clinton will have to spend far less time in the Senate, a move that, aides say, she had hoped to put off until later in the election season, considering she was just reelected to a second term last fall. Clinton's Senate record — and particularly the skill she has shown working across party lines — has been her answer to those who say she is too polarizing to be elected. But as former majority leader Bob Dole and others have learned, the chamber isn't an ideal base from which to run a Presidential campaign.

Clinton's challenges go well beyond money, though. She also has what Obama's handlers are calling an "enthusiasm gap." The New York State Senator still leads in most polls, but the latest Gallup survey found that 52% of respondents have an unfavorable view of her. Her favorable rating has dropped 13 percentage points since February, to 45%, and has been below 50% in each of the past three Gallup surveys. By comparison, Obama and former Senator John Edwards, her two strongest rivals, registered 52% favorable ratings, and — more significantly — their unfavorables were at about 30%.

So Clinton is lavishing more attention on groups like women, whom she considers her natural constituencies. After radio host Don Imus got fired for his controversial remarks about the Rutgers women's basketball team, Clinton accepted a long-standing invitation to speak on the campus about women's equality. And both she and Obama are aggressively courting African-American voters, who are torn between their loyalty to the Clintons and their excitement over the prospect of the first black President. As Obama was telling his life story during a recent appearance with Al Sharpton in New York, Sharpton's cell phone rang. "Is that Hillary calling?" Obama joked. "Breaking my flow?"

Bill Clinton will also put in more time on the trail, as well as in smaller sessions with donors and activists. Part of his job has been to make the case that his wife and Obama aren't so different in their records on Iraq: though Obama opposed the Iraq invasion as a Senate candidate, the former President argues, Obama's voting on the war has been virtually identical to Hillary's in the Senate. Bill has "verged on feckless in this respect," grumbles a leading Democratic fund raiser who has defected from the Clinton camp to Obama's. Both Clintons have made the case to potential fund-raisers that the U.S. will probably suffer a terrorist attack on the scale of 9/11 after the next President is sworn in — and that Hillary is the only Democratic candidate capable of handling such a crisis because of her Senate Armed Services Committee tenure and her years in the White House.

Hillary Clinton is also banking on the grueling schedule of debates, which is "where she will shine," says a strategist. "This will be her strongest point. She knows this stuff inside out." But her team says she is not yet ready to begin challenging Obama directly on his lack of specificity. That's because going on the attack could further boost her negatives and create an opening for Edwards, who has offered far more detailed plans than she has on issues like health care. "They are worried about both Obama and Edwards," says an outside adviser. "They think if Obama flames out, Edwards rises." And if that happens, Hillary's team will have to consider a course correction once again.