WASHINGTON — Senator McCain padded his commanding delegate lead in the Republican presidential race today and urged conservative critics to cut him some slack. In a Democratic surprise, Senator Clinton disclosed she’d lent $5 million to her cash-short campaign.

“And I think the results last night proved the wisdom of my investment,” the former first lady said.

The competition for Republican delegates was a runaway.

Nearly complete returns from Super Tuesday left Mr. McCain with 707 delegates, nearly 60% of the 1,191 needed to win the nomination at the national convention in St. Paul, Minn., this summer.

A former Massachusetts governor, Mitt Romney, had 294, a former Arkansas governor, Michael Huckabee 195, and Rep. Ron Paul of Texas 14.

Despite steadily lengthening odds, neither Mr. Romney nor Mr. Huckabee offered any hint they were ready to exit the race.

Mr. McCain, the Arizona senator, said the nomination was his, though, and added he recognized there was work to be done to unify the party after acrimonious campaigning.

“I do hope that at some point we would just calm down a little bit and see if there’s areas we can agree on,” he said, one day in advance of an appearance before conservative activists who have shunned his candidacy.

The Democratic delegate count lagged, the result of party rules that shunned the type of winner-take-all primaries in states such as New York and New Jersey that helped Mr. McCain build his advantage.

Yesterday’s busiest primary night in history, Mrs. Clinton and Mr. Obama were separated by 26 delegates, with 139 yet to be allocated.

Overall, that left Mrs. Clinton with 1,045, more than half of the 2,025 needed to secure the Democratic nomination. Mr. Obama was right behind with 960.

With little time to rest, both Mr. Obama and Mrs. Clinton pointed toward the next contests, primaries in Louisiana, Maryland, Virginia, and the District of Columbia plus caucuses in Nebraska, Washington, Maine, and the Virgin Islands in the next week. In all, those states offer 353 delegates.

At a news conference in Chicago, Mr. Obama claimed victory on Super Tuesday, saying he had won more states than the former first lady for the day and would wind up with more delegates by the time all were tallied.

He bluntly took issue with the suggestion that he, more than she, could be brought down by Swift Boat-style criticism in the fall campaign.

“I have to just respond by saying that the Clinton research operation is about as good as anybody’s out there,” he said.

“I assure you that having engaged in a contest against them for the last year that they’ve pulled out all the stops. And you know I think what is absolutely true is whoever the Democratic nominee is the Republicans will go after them. The notion that somehow Senator Clinton is going to be immune from attack or there’s not a whole dump truck they can’t back up in a match between her and John McCain is just not true.”

He said he would be campaigning in all the states in the next round of primaries and caucuses.

Mrs. Clinton said she would contest Mr. Obama everywhere, although senior aides conceded Mr. Obama would have more to spend on ads.

“We will have funds to compete,” Clinton’s chief strategist, Mark Penn, told reporters in a conference call. “But we’re likely to be outspent again.”

A few hours later, the campaign’s communications director, Howard Wolfson, said the senator had loaned money to her campaign late last month.

Officials with both campaigns have said Mr. Obama raised $32 million in January and Mrs. Clinton $13.5 million, a significant gap between the two that allowed Mr. Obama to place ads in virtually every Super Tuesday state and get a head start on advertising for the next primaries and caucuses.

Among Republicans, there was speculation that Mr. Romney was contemplating a withdrawal. He offered little hint of his plans, announcing only that he would appear before conservatives and make a speech to Maryland Republicans tomorrow.

The wealthy former businessman has spent an estimated $40 million to $50 million in personal funds to finance his campaign, but he ran something of a scaled-back effort in several Super Tuesday states.

He emerged with a string of victories in caucuses, but won primaries only in his home state of Massachusetts and in Utah.

Mr. Huckabee scored a series of Southern victories on Super Tuesday and has said he will stay in the race until someone has enough delegates to clinch the nomination.

Interviewed on CBS, Mr. Huckabee sidestepped when asked whether he might be an irresistible vice presidential running mate on a ticket headed by Mr. McCain. “I still want to be the irresistible choice to be the president,” he said.

Mr. McCain wasn’t talking on that subject, but the vote totals and exit polls made it abundantly clear that he was weak where the former Arkansas governor was strong — in appealing to evangelical conservatives in the Bible Belt.

A Louisiana primary and caucuses in Kansas on Saturday offer an inviting target for Mr. Huckabee, who has demonstrated a strong appeal to social conservatives.

Mr. McCain didn’t say so, but there is ample evidence he is pleased to have Mr. Huckabee in the race. In state after state, Mr. Huckabee has divided the anti-McCain vote with Mr. Romney, preventing the former Massachusetts governor from emerging as a more serious threat.

Yesterday, Mr. McCain’s delegates at the West Virginia convention swung over to support Mr. Huckabee at the last minute in a successful maneuver designed to deprive Mr. Romney of a victory.