Romney wins primary races in Michigan, Arizona

Mitt Romney scored a hard-fought victory in his native state of Michigan and won handily in Arizona, slowing the advance of his top Republican presidential rival Rick Santorum and gaining precious momentum ahead of a key set of primary contests next week.    

Romney's sweep of Tuesday's contests marked the latest turn in a turbulent Republican primary campaign, and could cement his status as his party's front-runner to challenge President Barack Obama in the November presidential election. But he fell short of landing the knock-out punch needed to stop his top opponent in his tracks.      

Romney is viewed as the candidate best positioned to beat Obama, and he has the backing of much of the Republican establishment as well as more campaign funds and a stronger organization than his primary rivals. But Santorum has captured the heart of the party's conservative base, which has no doubt about the authenticity of his views on social issues such as abortion and considers Romney too moderate and inconsistent.    

"We didn't win by a lot but we won by enough, and that's all that counts," Romney told cheering supporters in Michigan on Tuesday night.      

"On to the March contests," he said, looking ahead to next week's 10 Super Tuesday races that could go a long way toward determining the Republican who will take on Obama.

AP