Republican John McCain last night called on disgruntled conservatives to support his presidential bid after main rival Mitt Romney ended his struggling campaign.
Mr McCain assured a conference of conservative activists he was one of them, citing his commitment to win in Iraq, halt Iran's nuclear ambitions and rein in the federal government, while drawing sharp contrasts with potential Democratic opponents Hillary Clinton or Barack Obama.
"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," the Arizona senator said.
"And I am acutely aware that I cannot succeed in that endeavour, nor can our party prevail over the challenge we will face from either Senator Clinton or Senator Obama, without the support of dedicated conservatives," he said.
He said Mr Obama and Mrs Clinton would create a disaster in Iraq, fail to recognise the threat posed by Iran and weaken the fight against Islamic extremists. "Their resolve to combat it will be as flawed as their judgment," he said.
Mr McCain (71) has built a strong lead in delegates to the party's nominating convention. But the former Vietnam prisoner of war has become a target of critics on the right for his moderate views on illegal immigration, his votes against President George W. Bush's tax cuts in 2001 and 2003, and his labelling in 2000 of some religious conservative leaders as "agents of intolerance."
Mr McCain's speech, which drew boos on the topic of illegal immigration, came several hours after Mr Romney's surprise announcement at the conference that he was ending his run to allow Republicans to focus on the November election.
Senator John McCain
"I feel I have to now stand aside, for our party and for our country," the former Massachusetts governor told the shocked crowd, some of whom shouted "No, no!" in response.
Mr Romney pulled out after losing 14 of 21 states on Tuesday, the biggest day of US presidential voting ahead of November's election.
Former Arkansas Governor Mike Huckabee, who won five states on Tuesday, remains in the race but will have a difficult task overcoming Mr McCain, who has secured more than 700 of the 1,081 delegates needed to win the nomination.
"This is a two-man race for the nomination, and I am committed to marching on," Mr Huckabee said after Mr Romney's withdrawal.