AND THE SUCCESSOR IS...

By JEFFREY H. BIRNBAUM/WASHINGTON

Senator William Roth of Delaware is a creature of habit. He once took a liking to what his aides agreed was an ugly brown corduroy suit, so much so that he wore it even on the hottest summer days. His staff finally had enough of the monstrosity. An aide confronted him: "Senator, the bad news is there was a fire at your house." Before the horrified Roth could say a word, the aide continued, "The good news is it was confined to your closet." The brown suit disappeared. But he still sticks to an offbeat wardrobe that seems a fitting accompaniment to his store-bought hairpieces.

Roth remains a creature of legislative habits too. As Bob Packwood's successor as chairman of the Senate Finance Committee, Roth is as hot to cut taxes as Packwood was cautious. Probably best known for his role in the deficit-ballooning, Kemp-Roth tax cut of 1981, which slashed rates 25% across the board, Roth says he is determined to stage an encore performance, planning to cut estate and capital-gains taxes and provide tax relief by expanding individual retirement accounts and creating a new tax credit for families with children. He also wants to overhaul the federal income tax. His chief aims are simplification and increased incentives for saving and investment. Says he: "I can't tell you how many times Congress has said it would simplify the income tax, and then added 500 pages of complexity that nobody understands." In pursuit of simplification, his Governmental Affairs Committee last week drafted a bill to dismantle the Commerce Department.

Some fellow Senators, however, wonder whether Roth, 74, is up to the Finance Committee job. He has always been strong on big ideas but weak on the details. Roth goes nowhere without an aide conversant in the substance of even his pet issues. When visitors come to his office, he has demonstrated more interest in showing them the framed photos of his beloved Saint Bernards than in twisting arms and cutting deals. But Republicans must deliver on their promise to bring the budget into balance or face an even angrier electorate. And the Finance panel is where much of that legislation comes from. The stakes for the g.o.p. are sim ply too high for the new chairman to be allowed to fail. Roth acknowledges he must rely on majority leader Bob Dole. "I would certainly work closely with the leadership,'' he says. "Dole in particular.''

--By Jeffrey H. Birnbaum/Washington