John McCain to endorse Mitt Romney Senator John McCain will endorse Mitt Romney for president, a source close to the senator says. Former Republican presidential nominee John McCain will endorse Mitt Romney for president, a source close to McCain confirms to CBS News. Following media reports that the endorsement would take place Wednesday in New Hampshire, former Pennsylvania Sen. Rick Santorum told CNN "it's fine," adding that he is surprised McCain had not made his support for Romney official already. Romney endorsed, and later campaigned for, the Arizona senator in the 2008 presidential election after announcing his own withdrawal from the race. Still, the two were fierce competitors in the days leading up to Romney's withdrawal. Santorum pulled off a stunning come from behind performance in Tuesday's Iowa caucuses, running in a virtual dead heat with Romney in the closest Iowa contest since the modern caucuses were formed in 1976. Santorum endorsed the former Massachusetts governor in 2008, saying he had to do everything possible to keep McCain from being president. Last month, reports signaled that McCain "might" endorse a Republican candidate "several months later on." McCain was widely expected to throw his weight behind Romney.