Robert E. Bauman says he is a new man: sober, slim, happier than he's been in years -- and possibly ready for a political comeback.

Once the razor-tongued rising star of the Republican right, Bauman pleaded not guilty last fall to charges of soliciting sex from a 16-year-old boy and underwent court-ordered rehabilitation. After admitting to "twin compulsions" of alcoholism and "homosexual tendencies," he lost his bid for a fourth term in Congress.

For the workaholic representative from Maryland's conservative Eastern Shore, it was seemingly the end of a 28-year career in politics. He left Capitol Hill a chastened man.

Bauman spent two months after the election as a consultant to House Minority Whip Trent Lott (R-Miss.) and then went home to his wife and four children in Easton, vowing to "live one day at a time." Since then, he says, he has consumed nothing stronger than diet tonic water, joined his kids in everything from horseback riding to high school sports banquets, read Karl Menninger and Sherlock Holmes and kept busy as a $100-an-hour lawyer.

He also has sent out 10,000 letters to supporters around the country, quoting fan mail from Puerto Rico and California ("Don't let your troubles get you down. God means for you to have a significant role in the history of this great nation. . . .") and wondering: "Bob Bauman has a big decision to make and it must be made soon. Should I run again for the House of Representatives in 1982?"

Bauman, who began his career on the Hill as a 15-year-old page and made his name as the watchdog of the House, has not exactly retired from politics. In the last two months, he has attended seven Lincoln Day dinners, the National Conservative Political Action conference in Washington ("I got a standing obation," he boasted later), a reception held in his honor by the Maryland Federation of College Republicans, several meetings among local Republicans who have urged him to seek office again and one cemetery dedication. The first Bauman for Congress Committee has already been formed, by an insurance man from La Plata.

Maryland Republican Party Chairman Allan Levy talked with Bauman at a few of those Loncoln Day dinners, and he says, "Bob Bauman seemed at peace with Bob Bauman. If his health is okay, you'll probably see Bob Bauman running for Congress again."

"Politics has always been my life," Bauman said last week.

Bauman hasn't just been writing to the voters. He also has sent letters to all the Republican members of Congress, asking for help with his 1980 campaign debt and explaining why he needs their money: ". . . . Retiring this debt is crucial to me because so many people in my district [and in Congress] have been urging me to run again. Before long I must have a professional poll taken and a war chest for 1982 must be assembled if I decide to go."

Bauman says that about 25 members of Congress sent him checks, about 50 wrote letters saying they'd like to give but don't have the funds and "not less than 100" have urged him to run again.

"I certainly don't want to run if there's no chance of winning," he said last week. "But I certainly would consider it if the potential is there. After all, I got 48 percent of the vote under the most trying circumstances."

In the House, Bauman shined as a brilliant parliamentarian, and was known for his retorts and putdowns. It is inevitable, then, that any talk of a possible Bob Bauman comeback provokes some tart debate. From his 32-year-old successor, Roy Dyson: "Sometimes I don't think he's a rational person."

Dyson said that hints of another race against Bauman inspire him to run harder. "Instead of 16 hour days, I work 18 hour days."

"I hope he wears out his work boots," sniped Bauman, referring to Dyson's campaign trademark.

Bauman remarked further that Dyson, a lumber and hardware man from St. Mary's County, has a congressional office in an undesirable location. "He didn't show up to draw his room number, and that's why he wound up in the basement of the Longworth building, just over the cafeteria air vent."

Dyson countered that his office, located in Room 1020 of the Longworth Building on Independence Avenue, is "beautiful" and nowhere near the cafeteria air vent or the basement. "Most of the people who come here are impressed," he said.

The poll to assess Bauman's chances of winning back the confidence of the hard-working, Godfearing, tradition-loving voters along Maryland's Eastern shore will be completed within the next month. Whatever the results, Bob Bauman, lawyer and self-proclaimed family man, says he won't be idle. He says voters still telephone him, wanting help with such things as Social Security checks, utility bills and passports.

He reads 20 newspapers a day, including all of the ones within his district. With his wife Carol commuting to her job as a high official of the Department of Energy in Washington, he does his share of the grocery shopping. He says he still talks with important people ("I was on the phone with the White House this morning," he said), and is still involved the American Conservative Union and the Young Americans for Freedom.

And he is even dabbling in some legislative work. When his 15-year-old daughter Genie, who was elected to the mock House of Delegates in Annapolis this year, needed help with her antiabortion bill, she knew the person to turn to for help -- her father.