This year has increased visibility for Frist, 50, who gained recognition and goodwill among key Republicans during his extremely successful stint as the head of the GOP Senatorial Campaign Committee. A Harvard-trained heart surgeon Frist votes a very conservative line on most issues, but is known to depart from his party's position on issues with a scientific bent, including stem cell research and extending care for AIDS patients. He is the only physician currently serving in the Senate, and his colleagues often depend on his opinion when considering votes on medical issues.
Well liked and respected within the GOP and beyond, Frist is rumored to be mulling a 2008 presidential run. In the meantime, he maintains a very close relationship with the current White House, and particularly with presidential advisor Karl Rove. The Associated Press reports there are some Republicans who fear Frist may be perceived as simply a "yes man" for the President's agenda, and others who worry his proximity to Bush could make him especially vulnerable to partisan attacks.
While it certainly has the benefit of momentum, Frist's candidacy may not go unchallenged; Pennsylvania Senator Rick Santorum is believed to be considering a run for Lott's spot as well. Santorum, one of the Senate's most consistently conservative voices, does not share Lott's or Frist's predilection for compromise. A Senate under his leadership would likely be a more adversarial and far more friendly to the conservative wing of the GOP than what would emerge under Frist.