, the Republican presidential nominee in 2008 and a two-time winner of the New Hampshire primary, plans to endorse
on Wednesday in the nation's first primary state, sources close to the Arizona senator confirm.
The expected backing of the Arizona senator would lend more establishment support to Romney's campaign and potentially add to the sense of momentum following his ultra-narrow, eight-vote victory in the Iowa caucuses Tuesday.
McCain had said last year that he would follow in the tradition of past Republican nominees and not back one of the candidates in the contested primary fight. But he did occasionally wade into the race on his Twitter feed, making statements supportive of Romney or critical of other candidates.
Most recently, he supported Romney's decision to skip a planned debate that would have been hosted by
Four years ago McCain skipped the Iowa caucuses and focused his efforts on New Hampshire, where he edged Romney by more than 5 percentage points in a victory that put him on the path to the nomination.