Senator John McCain clinched the Republican presidential nomination on Tuesday, while his rival Mike Huckabee dropped out of the race.

Senator John McCain and his wife, Cindy, greet supporters in Dallas on Tuesday night.
(Gerald Herbert/Associated Press)

McCain, 71, surpassed the requisite 1,191 Republican delegates as voters in Ohio, Vermont, Rhode Island and Texas put him over the threshold, according to a tally by the Associated Press.

The four-term Arizona senator, who has often been at odds with the party's right flank, is preparing to carry the Republican banner in the U.S. presidential election in November.

"I am very, very grateful and pleased to note that tonight, my friends, we have won enough delegates to claim with confidence, humility and a great sense of responsibility that I will be the Republican nominee," McCain told his cheering supporters at a speech in Dallas.

"The big battle's to come," he added, referring to the general election. "I do not underestimate the significance nor the size of the challenge."

McCain entered Tuesday's contests with 1,014 delegates, 177 short of what he needed.

On Tuesday he won all 17 delegates in Vermont, and at least 69 in Texas, 58 in Ohio and nine in Rhode Island, according to early returns. McCain also picked up about 30 endorsements from party leaders who will automatically attend the convention.

Only Texas congressman Ron Paul technically remains as a challenger to McCain, but it's now impossible for him to become the nominee. He has not indicated when he will concede but his departure is inevitable.

Official nomination coming in September

Republicans won't officially nominate McCain until early September at the Republican national convention in Minneapolis-St. Paul. McCain said in the meantime, he has no intention of resigning from the Senate, although it's something he will discuss with the party.

The Vietnam War veteran and former prisoner of war said he never believed he was destined to be president.

"I don't believe anyone was predestined to lead America, but I do believe that we were born with responsibilities to the country," McCain said. "I owe my country every opportunity I have ever had."

He noted that as president, he would be ready to lead the two wars the United States is fighting, in Afghanistan and Iraq.

"The next president of the United States must encourage the greater participation and co-operation of our allies in the fight against al-Qaeda and the Taliban in Afghanistan," he said.

Huckabee a 'great and fine and decent American'

Shortly after McCain's victory was declared, his chief remaining rival withdrew from the race. Huckabee, a former Arkansas governor, praised McCain in a speech in Texas.

Mike Huckabee drops out of the Republican presidential race in Irving, Texas, on Tuesday night.
(Matt Slocum/Associated Press)

"My commitment to him and the party is to do everything possible to unite our party, but more important, to unite our country so that we can be the best we can be."

McCain called Huckabee "a great and fine and decent American."

Democrats Hillary Clinton and Barack Obama, who are locked in a fierce battle to become their party's nominee, both congratulated McCain in speeches on Tuesday night and said they looked forward to spirited debates with him in the lead up to the U.S. election.

But Obama said he would be ready to counter McCain's vision.

"In this election, we will offer two very different visions of the America we see in the 21st century," he said. "John McCain may claim long history, straight talk and independent thinking, and I respect that, but in this campaign, he has fallen in line behind those very same policies that have ill served America."

"He has seen where [U.S. President] George Bush has taken our country and he promises to keep us on the very same course."

Bush to endorse McCain

Bush invited McCain to lunch at the White House on Wednesday, where the president will endorse the nomination. The two men will make a joint statement afterward.

"The president has said he looks forward to vigorously campaigning for the GOP and tonight it has become clear that the GOP nominee will be Senator John McCain," White House press secretary Dana Perino said Tuesday.

"Of course the president is going to endorse the GOP nominee, which is going to be Senator John McCain."

McCain unsuccessfully ran against Bush to become the Republican nominee in 2000.

McCain's triumph Tuesday came one month after Super Tuesday coast-to-coast victories gave him an insurmountable lead in the delegate hunt and forced another rival, Mitt Romney, to drop out of the race.

Romney endorsed McCain soon after.

With files from the Associated Press