Mitt Romney has enhanced his image as a front-runner by staying above the fray during a run of Republican debates, but Monday he sharply abandoned that approach to unleash a withering attack on the rival who threatens his claim to the nomination.

• Mitt Romney enters fray at Tampa GOP debate, unleashes attack on Newt Gingrich
• John Romano: Romney tries out the face of a fighter
• Florida up for grabs in GOP presidential race
• RNC 2012: Your guide to the Tampa convention
• PolitiFact.com: Previewing the Tampa GOP presidential debate

• More special reports