One major reason that senators make weak presidential candidates is that they usually have extensive voting histories, which can be cherry-picked by opposition researchers to smear the candidate with (some) of his own votes.
Given all the compromises, quid pro quos and procedural hijinks that go on in that whorehouse, I would bet that one could make any senator from either party look like a demon or a saint, pretty much at will.
On the other hand, you will notice how rare it is for the newt-haters to actually rely on his votes. They much prefer to float out offhand comments, attacks on his personal life, and the occasional brain fart, because his voting record does not support their efforts to smear him.
DING DING DING: We have a WINNER. You are exactly right, which is why I converted from Newt hater (well, never was a hater, just a doubter). Based on his brilliant debate performances and his attacks only being against the media and Obama - I sort of stepped back and analyzed what he did in the House. And he was a solid, if not perfect, conservative. He also forced Bill Clinton to govern to the right. In a field of imperfects, he has actually accomplished more for conservatism than anyone else by far. That, and talking the talk the best, is why I moved to support him. His conservative cred is higher than Santorums.