Locked in a close race, Mitt Romney is predicting victory in Michigan's critical primary. He's hoping to prevent an unexpected loss to rival Rick Santorum in the state where the former Massachusetts governor was born and raised.

Romney has spent the past five days campaigning hard for votes in Michigan's primary on Tuesday, selling himself as a native son steeped in the auto industry that has defined the state for decades.

He has a strong lead in Arizona, which also votes Tuesday.

Romney has had to play catch-up in Michigan after losses to Santorum on Feb. 8 in Minnesota, Missouri and Colorado. A loss in Michigan would seriously damage the campaign of the on-again, off-again front-runner and probably stretch an already lengthy GOP nominating contest even more.