Republicans in Michigan began making their choices in the presidential race on Tuesday, with native son Mitt Romney battling for political survival in a primary that could either revive or sink his campaign.
As the results roll in from Michigan, Democratic White House contenders Barack Obama, Hillary Clinton and John Edwards are scheduled to meet in an evening debate in Nevada, site of the party's next contest on Saturday.
The hectic schedule reflects the heightened intensity of the wide-open presidential race, as both parties choose candidates for the November election to succeed President George W. Bush.
Polls show Romney, a former Massachusetts governor who was raised in Michigan, running neck-and-neck with Arizona Sen. John McCain in a state where the ailing economy has moved to the top of the agenda.
A Reuters/C-SPAN/Zogby poll released early on Tuesday gave McCain a statistically insignificant 1-point edge, 27 percent to 26 percent, over Romney. Former Arkansas Gov. Mike Huckabee was third with 15 percent.
Romney needs a breakthrough win to keep his White House hopes alive after second-place finishes in Iowa and New Hampshire. A McCain win after last week's New Hampshire victory would thrust him into the front-runner's role heading into contests in South Carolina and Florida.
Asked in an interview on CNN if his campaign would recover if he failed to win in Michigan, Romney said: "Oh, sure."
"I'm not going to let four states, only four states, decide for 50 states who the nominee ought to be," said Romney, who has pumped tens of millions of his own dollars into the race but whose only victory so far was in sparsely populated Wyoming.
Wearing his lucky green sweater and clutching his lucky penny, McCain visited a polling place early in Traverse City.
"It's going to be a very close race," he told reporters who outnumbered voters at the polling site shortly after voting began at 7 a.m. EST (1200 GMT). "We're confident because of the enthusiasm at the town hall meetings and the rallies but we've got a long way to go."
Most of the state's polls close at 8 p.m. EST (0100 GMT on Wednesday) and results will begin rolling in soon afterward.
Democrats also will hold a primary in Michigan, but a dispute over the date of the vote led the national party to strip the state of its delegates to this summer's presidential nominating convention.
As a result, Obama and Edwards kept their names off the ballot and Clinton is the only top contender listed. None of the top Democrats have campaigned in the state since the dispute arose.