SIMI VALLEY, Calif. -- Once-crowded presidential fields shrank to two-person races yesterday, as John Edwards and Rudolph W. Giuliani abandoned their White House runs.
Edwards' abrupt withdrawal was unlikely to alter the Democratic contest, party strategists said, because his dwindling corps of supporters will probably split between Sens. Hillary Rodham Clinton and Barack Obama.
Tonight, the finalists meet for the first time in a head-to-head debate, with strategists predicting that the fight for delegates will extend beyond next week's Super Tuesday contests, to states such as Maryland, on Feb. 12, and perhaps for months afterward.
By contrast, the Republican race appeared to be rapidly nearing a climax, perhaps as early as Tuesday. Front-running John McCain continued to gain fresh momentum, as Giuliani folded his candidacy by endorsing the Arizona senator and California Gov. Arnold Schwarzenegger made plans to add his endorsement today.
Those actions helped feed a sense of inevitability that was rapidly building around McCain's candidacy. Adding to that perception, neither Mitt Romney's campaign nor McCain's has announced plans to initiate major Super Tuesday television ad buys.
That reluctance reflected the almost prohibitive cost of reaching voters in more than 20 states as well as a recognition that there might be little value in trying.
Speaking to a horde of reporters yesterday before a Republican debate at the Ronald Reagan Presidential Library, Giuliani praised McCain as "the most qualified candidate to be the next commander in chief."
Giuliani's decision to throw his support to McCain was a powerful assist, even though the former New York mayor and one-time Republican favorite never caught on with large numbers of primary voters. His support is concentrated among moderate Republican voters, who now are expected to shift largely to McCain.
That could be particularly important in New York, New Jersey and Connecticut, which hold primaries Tuesday. Taken together, the tri-state area represents the largest chunk of delegates one candidate could realistically expect to win next week. McCain already leads in polling in those states, and his Florida victory amplifies his chances for a sweep.
Giuliani indicated that he would campaign with McCain in New York and neighboring states, as well as in Illinois and California. Republicans in California said that Giuliani had built an effective campaign organization in the state, with the ability to reach voters by phone and get them out on election day.
By turning that machinery over to McCain, he'll fill a gap created by the senator's decision to abandon campaign activities in this state and many others last year after his candidacy nearly collapsed.
McCain's ability to win the nomination in the absence of a traditional infrastructure, assuming he does so, could emerge as one of the most remarkable aspects of his campaign. He won Florida, for example, without having a single paid staff member in the state, according to a top aide.
McCain is still scrambling to raise new money to compete against Romney, who has the ability to provide his campaign with needed funds, merely by writing a check from his own considerable bank account. But there were indications last night that the former Massachusetts governor may no longer be willing to do so, with one adviser saying that Romney might decide to rely on news media coverage to get his message across between now and Tuesday.
Meanwhile, McCain might seek a knockout blow in Romney's home state, where the senator plans to campaign this weekend and aides see a chance of a victory.
Romney faces serious difficulties in trying to keep McCain from pulling away, in spite of his advantage in campaign funds. He has outspent McCain in every state but has won only one major contest, in his native Michigan.
Romney's most recent arguments against McCain - that the veteran legislator is the wrong man to change Washington and that Romney's business background makes him better suited to preside over the U.S. economy - haven't worked.
Romney is also hurt by the continued presence in the race of Mike Huckabee, who ranks third in delegates and is no longer a serious contender for the nomination, according to Republican politicians.
But Huckabee, a former Arkansas governor and Baptist minister, is still popular with many religious and social conservatives. His continued presence in the race attracts votes that otherwise would largely go to Romney, especially in next week's Southern and Southwestern primaries and rural districts of states as diverse as California, Illinois, Minnesota and Missouri.
The fourth man in the race, Texas Rep. Ron Paul, has failed to make a mark in primaries and caucuses, despite raising large amounts of money from his dedicated cadre of supporters.
McCain, in brief remarks accepting Giuliani's endorsement, looked ahead to November as he tries to get a badly fractured party to coalesce behind him.
In his victory speech Tuesday night, he drew references to Reagan, who remains the gold standard for Republican conservatives. McCain tied himself, and his experience as a captured U.S Navy flier in a North Vietnamese prison, to Reagan, recalling the "whispered conversations and tap codes about the then-governor of California, who stood by me and my comrades."
Last night, the Republican candidates met for the 16th and perhaps last time in a primary debate that reflected the changed dynamics of the race.
McCain laughed off Romney's initial attacks, after the former governor said McCain was not a true conservative and noted that The New York Times had endorsed his candidacy.
McCain retorted that he had also received the backing of Romney's hometown dailies, including "the very conservative Boston Herald," newspapers that, McCain said, know Romney best.
"I'll guarantee The Arizona Republic will be endorsing me, my friend," McCain said at the event, co-sponsored by CNN, the Los Angeles Times and Politico.
The debate consisted largely of recycled bits of campaign stump speeches and issues that have been aired repeatedly at previous forums.
McCain, Romney and Huckabee - who objected at one point that "this isn't a two-man race" - did break new ground on an issue of importance to environmental advocates. All sided with California and other states, including Maryland, in their dispute with the Bush administration, which has blocked the states from imposing strict new limits on tailpipe emissions from motor vehicles.
"I applaud [Schwarzenegger's] efforts and that of other states in this region and other states across America to try to eliminate the greenhouse gas emissions that are causing climate change," said McCain, whose views on global warming are among those that have drawn the ire of conservatives and a legion of right-wing talk show hosts.
Democrats will hold their California debate this evening, the first one to feature just two candidates, Obama and Clinton. Mike Gravel, a former Alaska senator, has not officially ended his campaign but has won no delegates.
Edwards, in ending his campaign, did not endorse either of his remaining rivals and is unlikely to do so immediately, aides said. In a graceful nod to the remaining contenders, he said he was leaving the race "so that history can blaze its path," with the presidential nomination of either the first woman or African- American by a major party.
Edwards campaign manager Joe Trippi said that it had become clear, after Edwards' third-place finish in his native South Carolina, a state he won four years ago, that he no longer had a feasible path to the nomination.