As the Senate's only doctor, Bill Frist (search) became the go-to guy on health care and was diagnosed as having the bedside manner needed in a majority leader. But now there's another doctor on the scene - newly elected Oklahoma obstetrician Tom Coburn (search) - and while the two Republicans share a passion for medicine, they are far apart on how they approach politics.

Not one to shy away from challenging the status quo, Coburn is trying to change ethics rules that he says prevent him from practicing medicine on weekends and during breaks. Coburn says he only wants to recover his costs, but Senate rules generally bar lawmakers from earning outside income.

Frist, a heart-lung surgeon before coming to Congress, sometimes volunteers his surgical services, including on trips to developing countries, but has not sought compensation. While involved in the discussions on Coburn's request, he has declined to offer his view of it.

Both men came to Washington as part of the 1994 Republican Revolution and refer to themselves as citizen legislators. Each has promised to serve only two terms and each has talked about returning to medicine. Frist, however, is also viewed as a likely presidential contender in 2008.

Coburn says he must continue to work as a physician so that the job will be there when he leaves the Senate. While he was in the House, he also found that continuing to practice medicine was a good way to stay connected with voters back home.

"I got to hear straight from the horse's mouth things I never would have heard just as a congressman," he said in an interview.

Coburn was an outspoken maverick during his six years in the House and was part of an effort to oust former House Speaker Newt Gingrich for compromising with Democrats and not pushing a conservative enough agenda.

He "drove House leaders crazy," said Norm Ornstein, an analyst with the American Enterprise Institute (search) think tank, adding that there's still some lingering bitterness.

In Coburn's Senate race against former Democratic Rep. Brad Carson last year, both candidates ran scads of negative television ads. One Carson ad raised a woman's allegation that Coburn sterilized her without her permission, a charge Coburn denied.

House Speaker Dennis Hastert publicly predicted Coburn would lose. It may not have helped that in a book he wrote, Coburn described Hastert as needing a "spinal transplant" to rein in government spending.

Rep. Zach Wamp (search), R-Tenn., calls Coburn a close friend and a "take-no-prisoners, conservative ideologue."

"Senator Coburn may be a nightmare for some people, because he will not cave in," Wamp said. Under Senate rules, a lone senator has much more power to block legislation than a rank-and-file House member.

Frist is quite different. With no political experience prior to winning his seat in 1994, he quickly mastered Senate rules and protocol and endeared himself to GOP decision-makers. They turned to him two years ago to become majority leader when Mississippi Republican Trent Lott was ousted for praising the segregationist presidential run of the late South Carolina Sen. Strom Thurmond.

Frist also is seen as more moderate than Coburn even though both have conservative voting records. "He is basically still in the mainstream of his party, and Coburn definitely anchors the right," Ornstein said.

While Frist chooses his words cautiously, Coburn's comments often raise eyebrows.

For example, Coburn said, in reference to his anti-abortion and pro-death penalty stance, that he supports capital punishment for "abortionists and other people who take life." During last year's campaign he also talked about lesbianism running rampant in some Oklahoma schools and called state legislators in Oklahoma City "a bunch of crapheads."

Coburn and Frist do share some views on health care policy. Both advocate federal AIDS (search) funding and talk about the need to focus on disease prevention. Both want to put limits on malpractice awards they blame for driving up medical costs.

On other health issues, they're divided. Frist was an architect of the new law adding prescription drug benefits to Medicare. Coburn opposes it.

"I wouldn't have supported adding an entitlement for drugs," he said.

Coburn also is a vocal critic of earmarking, a common practice in which lawmakers insert pet projects into legislation to bring federal largess to their districts.

In one instance, while in the House, he refused an offer for money for projects back home - saying he viewed it as a bribe to support a bill laden with pork.

Frist hasn't been shy about using his influence as Senate leader to insert earmarks in spending bills to pay for projects such as a replacement for the aging Chickamauga Lock on the Tennessee River.

Prior to Frist's arrival in the Senate a decade ago, the last practicing physician in the chamber was New York Sen. Royal Copeland, who was in office in the 1920s and 30s. It's much more common for doctors to serve in the House, which now has 11 physicians.