And when it comes to launching an attack, Rick Santorum's rhetoric, in particular, has become white hot. From calling the president a "snob" to saying John F. Kennedy's 1960 speech makes him want to "throw up," Santorum is upping his ferocity almost as fast as he's increasing his poll numbers.
But while Santorum strikes a sharp tone, his rivals have been piling on him in return. From calling him a "fake" to a "big labor Republican," Ron Paul, Newt Gingrich and Mitt Romney are returning fire as the clock winds down in Michigan and Arizona, where primaries are currently underway, with polls closing tonight.
Here's a look at some of the mud that has been slung in this contentious race to the White House.