Republican National Committee chairman Bill Brock subscribes to keep his eye on the opposition. So do White House staffers, politicans, corporations, and even the publisher of a porn magazine. For $48 a year about 2000 students of politics receive a newsletter written by Alan Baron, whose decision to give up hardball politics for the pen is leaving maverick liberal Democrats without a familiar leader.

Baron, 34, was the wunder-kind of the young Democrats who briefly controlled their party in 1972 when George McGovern was the presidential candidate. Today, as owner of a newsletter and Washington editor of Thomas Morgan's new magazine, Politicks, Baron is finding writing can keep his Capitol Hill refrigerator stocked with the diet drinks - Diet Dr. Pepper and Tab - that are his trademark.

"I consider myself a journalist, not a politican anymore," says Baron, who consumes diet sodas to lose weight and, one suspects, out of gratitude for the time when cases of the stuff saved his life. While asleep downstairs in his townhouse last spring, Baron was awakened by sounds of explosions upstairs. Flames were filling his house and, Baron says, only the explosions of fifteen cases of diet soft drinks stored in anticipation of a government ban on saccharin allowed him to flee to safety.

Alive and forty pounds slimmer than his peak weight of 250 pounds, Baron still gets calls from political friends who want to huddle on Democratic strategy. As usual, Baron is standing just outside the winner's camp; he worked hard to stop Carter last year, so hard that he lost his job on McGovern's Senate staff for his extracurricular campaigning on behalf of Mo Udall. Baron blamed his sudden unemployment on pressure from Carter backers who didn't want McGovern to appear to be supporting Udall. Though he has written favorably about Carter's judicial selections and supported parts of his foreign policy, Baron remains "skeptical" about the President. That should not cause sleepless nights at the White House: the only winning candidate for whom Baron has worked was Harold Hughes during his Senate victory in 1968.

Does the old political bug tempt him? Can he keep his eyes on the typewriter? "I enjoy my boss now," Baron says. "Well, at least he is ideologically compatible."