(USA TODAY) — PHOENIX – The last time the four Republican presidential contenders met for a debate, former Massachusetts governor Mitt Romney was fending off a strong challenge from former House speaker Newt Gingrich in Florida and former Pennsylvania senator Rick Santorum was at about 15% in the national polls. What a difference three weeks make.

The momentum gained by Romney’s win in Florida was soon washed away by Santorum’s sweep of three Feb. 7 contests and subsequent rise in national polls.

The stakes for the debate in Mesa, Ariz., Wednesday night are high for the four remaining contenders: It is the last before the primaries here and in Michigan on Feb. 28, as well as the Super Tuesday contests March 6 in which a series of polls show Romney and Santorum battling it out for delegates.

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