Tuesday's primary in Florida is a key battleground in the race for the Republican US presidential nomination.

Florida considered important for several reasons, even though as a "closed primary" only two million registered Republicans can vote.

"A win in Florida gives you a pretty credible claim that you can stack up in the general election," said Adam Smith, political editor on the Tampa Bay Times newspaper. "Because, even though it's just Republicans voting here, it's a big diverse group of Republicans."

Al Jazeera’s Alan Fisher reports from Tampa, Florida.