"We're continuing campaigning and not taking anything for granted," McCain said in an Associated Press interview, still reluctant to call himself anything more than the front-runner. "I certainly think that we have enhanced our chances."
Only Mike Huckabee and Ron Paul remained in what has been a crowded and wide-open nomination fight for the past year. Both have narrow voting constituencies and are far behind in the hunt for delegates to the GOP's nominating convention this summer.
Romney's departure left McCain, whose independent streak rankles many in the Republican rank-and-file, poised to assume President Bush's position as the party standard-bearer. It was a remarkable turnaround for McCain, whose campaign was barely alive last summer, out of cash and losing staff.
"It is my sincere hope that even if you believe I have occasionally erred in my reasoning as a fellow conservative, you will still allow that I have, in many ways important to all of us, maintained the record of a conservative," McCain told a gathering of the party's influential right flank on Thursday a few hours after Romney appeared before the same group to announce he was suspending his faltering bid.
Said Romney, "I must now stand aside, for our party and our country.
"If I fight on in my campaign, all the way to the convention, I would forestall the launch of a national campaign and make it more likely that Senator (Hillary Rodham) Clinton or (Barack) Obama would win."
Romney's fate had been virtually sealed earlier this week when he failed to stop McCain's coast-to-coast Super Tuesday rout in presidential primaries; McCain and Romney spoke by phone Thursday but no endorsement was sought nor offered.
With weekend contests in Louisiana and Kansas up next, McCain has secured 707 delegates, more than halfway to the 1,191 needed to win the nomination. Romney has 294 and Huckabee 195. Paul, the libertarian-leaning Texas congressman, had only 14 - and no chance to catch McCain.
Huckabee is still mathematically viable in the race, but he will need a lot of help from Romney's supporters if he doesn't prevail in upcoming contests. Numbers aside, Huckabee also faces a steep challenge. The former Arkansas governor's primary constituency is Christian evangelicals, and he has won only in states where they dominate presidential contests - Iowa, Arkansas, Alabama, Tennessee, West Virginia and Georgia.
Privately, some Huckabee aides were eager to see their boss follow Romney's lead. Publicly, Huckabee showed no sign of backing down.
"I still believe that this thing is a long way from being settled. And, now that the field is down to two, our chances have substantially improved," he said in New York City.
The only other way Huckabee could seize the nomination is if conservative complaints about McCain turn into a full-scale revolt.
But that doesn't appear to be happening, if McCain's reception at the Conservative Political Action Conference was any indication.
Activists there seemed resigned - if not pleased - at the prospect of McCain's nomination.
Other Republicans said the fight was effectively over, and that Huckabee appeared to be angling more for a vice presidential slot than the top of the ticket.
"John McCain's going to Disney World," said Dan Schnur, an unaligned GOP strategist who worked on McCain's failed presidential campaign eight years ago. "Even if every social conservative in the Republican Party turns out for Mike Huckabee in the remaining primaries, he just doesn't have the credentials as an economic and national security conservative to pull this off."
As it became clear that McCain was the likely nominee, he won the support of several high-profile conservatives and members of the Republican establishment. During a vote on the Senate floor, almost every Republican lined up to shake his hand and congratulate him.
"It is now time for Republicans across the country to unite.
Together, led by Senator McCain, we will work for a better, safer, stronger America," said Ken Mehlman, a former Republican National Committee chairman.
McCain also collected the backing of former Virginia Sen. George Allen, who appeared with him at the conservative conference speech, and Texas Sen. John Cornyn. whom McCain has had heated words with over immigration.
South Carolina Sen. Jim DeMint, who had endorsed Romney, said conservatives "spent a lot of time criticizing Senator McCain and not rallying around a candidate that could take us to the presidency." Now, DeMint said, conservatives must "empower Sen.
McCain to carry our conservative values."
"We need him as much as he needs us," DeMint said.
Still, many conservatives remained skeptical, indicating the challenge ahead for McCain as he tries to turn out the Republican base come the fall race against Clinton or Obama.
"Most conservatives will vote for him. But 'most conservatives' is not enough to win the election, it's not enough to secure your base," said David Keene, the chairman of the American Conservative Union.
Gary Bauer, a prominent conservative and former presidential candidate, indicated that uniting the party was a two-way street, saying: "Senator McCain will have to reach out to conservatives, and conservatives importantly will have to reach out to Senator McCain."
Some offered an even more dour view.
"The Republican Party has left the moral conservative base adrift," said Jerome Corsi, a conservative activist.
Undeterred by such skepticism, McCain looked ahead to the fall campaign and saw his speech as a starting point to unite the GOP.
"I know I have a responsibility, if I am, as I hope to be, the Republican nominee for president, to unite the party and prepare for the great contest in November. And I am acutely aware that I cannot succeed in that endeavor, nor can our party prevail over the challenge we will face from either Senator Clinton or Senator Obama, without the support of dedicated conservatives," McCain said in a speech greeted alternatively with boos and cheers.
After it, McCain told the AP: "There's a lot of work to do. But I thought this was a very good beginning and I'm confident by this reception that we can continue successfully to unite the party."
