Mitt Romney gave John McCain a Valentine’s Day endorsement yesterday, declaring his one-time Republican presidential rival to be a man “capable of leading our country at a dangerous hour”.

His public backing, just days after he dropped out of the race for the candidacy, brings an end to the rancour that often characterised their relationship in bitterly fought primaries this year.

“Even when the contest was close and our disagreements were debated, the calibre of the man was apparent,” the former Massachusetts Governor said.

Mr McCain, standing next to Mr Romney at a joint press conference in Boston, replied: “Primaries are tough. We know it was a hard campaign and now we move forward. We move forward together for the good of our party and the nation.”

He even thanked Mr Romney — whom he had previously accused of propagating distortions — for fighting an “honourable campaign” that had “helped me become a better candidate”.

He promised that they would now travel across America together proclaiming their new message of unity.

Mr Romney collected 280 delegates before quitting last week and his endorsement may persuade many, if not all, to rally behind the Republican front-runner, who is closing in on the 1,191 he needs to clinch the nomination.

Mr McCain still faces opposition from conservatives who regard his maverick stances on issues such as immigration, tax cuts, campaign funding and the environment with intense suspicion.

Although he has always had good relations with his remaining opponent, Mike Huckabee, the former Arkansas Governor refuses to bow out of the race, saying: “I’ve nothing else to do.”

Mr Huckabee, who is briefly breaking from the campaign trail tomorrow to replenish his bank balance with a lucrative speech in the Cayman Islands, insists that he will continue fighting until it is mathematically impossible to stop Mr McCain.

“I’m the leader of the ‘not yet’ movement and that’s just fine,” he said cheerfully yesterday. “Right now there’s a great big ‘me too’ crowd coming together [for McCain]. There’s a lot of folks in the Establishment of the party that is not now wanting to be left out.”

The Baptist preacher has a strong appeal to evangelical conservatives and even defeated Mr McCain in two out of three states that chose delegates last weekend.

Mr Romney’s decision to settle his differences with Mr McCain may reflect his long-term ambition to stand for the presidency again. The Republican front-runner is 71 and, if he won November’s election, would be the eldest man to win a first term in the White House.

The Republican Party knows that it could yet capitalise from a nine-month period of effective unity while the Democrats continue to fight for their nomination.

Yesterday they helped to push Mr McCain’s signature issue of national security further up the political agenda by staging a walkout at Capitol Hill in protest at a decision to debate sanctions against former White House aides rather than measures to improve intelligence surveillance of terror suspects.

“We have space on the calendar today for a politically charged fishing expedition, but no space for a Bill that would protect the American people from terrorists who want to kill us,” John Boehner, the House of Representatives Minority Leader, said.

“Let’s just get up and leave,” he told his colleagues.

President Bush also pressured the House to complete the legislation giving the Government more leeway to eavesdrop on phone calls and e-mails, even threatening to postone today’s trip to Africa if congressional Democrats did not co-operate.

Times Recommends

• No cause for celebration in crushed Sarajevo
• Jazz funeral for the final victims of Katrina
• French fined for 'insulting' civil servants