TAMPA, Fla. (AP) — Mitt Romney embraced a killer instinct and leveraged a dominant political machine to crush chief rival Newt Gingrich in Florida's Republican presidential primary.Romney appeared beaten down when he came to Florida after Gingrich had trounced him in South Carolina. The former House speaker's triumph fueled a wave of momentum that threatened to unite anti-Romney conservatives.Recognizing the threat, Romney had hatched a new strategy even before the South Carolina loss was official.At its core was the end of nice-guy Romney, the man who had usually saved his sharpest barbs for President Barack Obama and let his allies run the attack ads. From the start of the Florida campaign, voters witnessed Romney's new go-for-the-jugular approach on their television sets, debate stages, and even at Gingrich's campaign stops.