So Gingrich, Santorum, and Paul are all candidates for the Republican nomination presently, and all in the 10-25% range in terms of their fraction of supporters. Ron Paul's support nationally is probably in the 15% neighborhood. Any one of these 3 can only hope to win the presidency with the support of a substantial fraction of the voters who presently support one of the other two.
So what does Gingrich do? He calls Paul's supporters dangerous and way out of the mainstream. Riddle me this, how large of a fraction of the population, by definition can be 'Way out of the Mainstream'? This is damned stupid of Gingrich, there's zero need for him to pile on at this point considering the massive media barrage against Ron Paul and insulting Ron Paul's supporters is doubly stupid. Many of them are smart and observant enough to actually notice.
What does Santorum do? Calls Ron Paul 'disgusting'. This is damnably stupid also, although not QUITE as stupid as Gingrich's move. This will probably only mortally piss of maybe half of Paul's supporters, as opposed to nearly all of them.
Look, I'm no stranger whatsoever to antagonism and conflict. When I have a disagreement I make no bones about it at all. But attacking people who could be your friends, or at least your co-belligerents is stupid, if only because you only have so much ammunition available on any given day. It is perfectly appropriate to attack competitors for a nomination, and a certain amount of rough & tumble is the expectation. Calling someone a flip-flopper, a tax & spend liberal, et al is all part of the game. But going meta and attacking their supporters is suicidal, at least from the standpoint of a desire to actually win elections.