WASHINGTON - Rep. Tom DeLay's ferocious reputation and flair for deal-making made him one of the most successful vote-counters in the modern history of the House. Now, as the new majority leader, DeLay may become either the Republicans' most potent weapon in Congress or a damaging liability.

With DeLay and his allies dominating a larger House Republican majority, his performance will help determine how well President Bush can move his agenda through Congress and pave the way for his 2004 re-election bid.

Few doubt that DeLay, a shrewd strategist with an impressive record, can help Bush score victories on top priorities, including a $670 billion tax cut, a reform of Medicare and welfare, and limits on damage awards from lawsuits.

But DeLay's aggressive style and higher public profile will play a bigger role in shaping his party's image. Democrats, who have long demonized him, can try to tie him more directly to Bush and paint his party as too conservative for mainstream America.

DeLay's allegiance to hard-liners in his party - potentially an asset for Bush as he works to solidify his core support for 2004 - could hurt the president's efforts to cut deals with moderates on popular initiatives. These include funding education and homeland security, and adding a prescription drug benefit to Medicare.

"As the leader, it's my responsibility to make sure that the legislation coming out of committees and coming out of the House is the right kind of legislation - the kind that reflects conservative values," DeLay said this week from his home in Sugar Land, Texas.

Still, DeLay's reputation for fierce conservatism might end up hurting Bush.

"Bush has a problem with the Republicans in the House, and DeLay is the symbol of it, and that is that Southern Republicans are more conservative, and the president needs those votes to get key legislation through," said James A. Thurber, director of the Center for Congressional and Presidential Studies at American University.

He "is leaning over backwards to that coalition and to Tom DeLay right now, and in doing that, he's going to have a problem with the more moderate Senate," Thurber said.

At the same time, DeLay seeks to centralize power in the fractious House by granting new authority to leaders and committee chairs and by rewarding loyalists. The strategy is similar to one Democrats used during their 40-year control of the House that ended in 1994.

DeLay has built up a reservoir of fealty throughout his party's House leadership ranks, which is peopled with his loyalists, including Speaker Dennis Hastert of Illinois and Rep. Roy Blunt of Missouri, DeLay's successor in the No. 3 slot of whip.

'The Hammer'

In demanding loyalty from colleagues, aides and lobbyists, DeLay keeps a close watch on them. As whip, he amazed friends and foes with his ability to deliver victories on contentious issues with tight vote margins, such as beating back a bid to federalize the entire aviation security work force.

He has done so with threats and ultimatums - earning him the nickname "The Hammer" - but also with the kind of sweet talk, bargains and treats, legislative and otherwise, that grease the wheels on Capitol Hill.

"He's tough when it comes to some of these waffling members," said Paul Weyrich, president of the conservative Free Congress Foundation.

But contrary to his reputation, DeLay is not all arm-twisting and intimidation. To secure a wavering lawmaker's vote, he might secure a project for his or her district or a campaign appearance by a top Republican.

"He's done a bazillion favors for people," says former Rep. Bill Paxon of New York, who is close to DeLay. "People respect him and are willing to bend over backwards to get him the vote, because he has done the heavy lifting and the tough jobs and the dirty work."

Few favors are too small. DeLay is known for serving pizza and barbecue in his Capitol office when the House is in session at dinnertime. He has arranged for private cars and flights to help lawmakers make important votes or party events.

He is equally devoted to - and demanding of - the web of lobbyists, interest groups and fund-raising operatives that influences Congress and elections.

DeLay has built alliances with business groups and trade associations and has helped deliver on some of their highest priorities, such as free-trade initiatives and tax cuts.

In return, he has insisted that they lobby lawmakers, donate money and even employ Republicans. (The House Ethics Committee admonished DeLay in 1999 for threatening to punish a lobbying group that hired a former Democrat as its president.)

By all accounts, DeLay's talent has been as a behind-the-scenes tactician and enforcer, and not as a unifying force in his party. Now that he's majority leader, allies say his role will be to help sketch a vision for the party's agenda.

"He's been an inside guy, and now he'll have to be out there, scheduling and passing the president's agenda and, in doing so, massaging it throughout the process so that it is successful," said Daniel J. Mattoon, a Republican lobbyist and ally.

Massaging is not known as DeLay's strong suit.

"His style is pretty confrontational - I don't think he tries to be a diplomat," said Rep. Steny H. Hoyer of Southern Maryland, the House Democratic whip.

DeLay, 55, whose neat dark hair and intense eyes match his domineering style, says his approach won't change.

"I'm organized and disciplined, and I am aggressive in trying to do what I think the American people want us to do," he said. "I have a new role, but I have the same goals. I won't change."

In the early 1970s, DeLay ran a pest extermination business in East Texas. Upset by environmental rules affecting the business, DeLay ran successfully for a seat in the Texas House. He spent six years there before winning election to Congress.

In Washington, DeLay wears his conservative ideology proudly. He opposes abortion rights. He has fought bitterly against government regulation, once branding the Environmental Protection Agency "the Gestapo." A born-again Christian, DeLay is famous for his public excoriation of former President Bill Clinton, whose impeachment DeLay relentlessly and successfully championed.

Colleagues and aides say his notoriety for twisting arms is exaggerated, but they acknowledge that he has been a polarizing figure - partly because it works to his advantage.

"He's cultivated it to some extent," said former Rep. Robert S. Walker of Pennsylvania, whom DeLay defeated for the post of Republican whip in 1994.

Among Republican leaders, Walker said, "there was a desire to have somebody who was a hard-nosed guy who was not only respected but also feared. It protected some of the other members of the leadership who didn't want to come out as strongly on certain issues."

Poor communicator

DeLay rejects the notion that he is a divisive figure.

"Some people think that when you're aggressive, you're mean-spirited - that's just not me," he said. The misperception comes partly, he adds, from his poor communication skills.

DeLay set a severe tone for his tenure as majority leader early on in the new Congress. He joined with Hastert to push through rules this month allowing top Republican leaders to dominate the chamber more thoroughly than in the past. They also eased the gift ban that had prevented lobbyists from, for example, catering meals for House members.

To install their allies to run committees, which produce the legislation the chamber considers, DeLay and Hastert also circumvented the traditional seniority system.

DeLay "is leading this effort to centralize power in the House," said Thurber of American University.

DeLay and Hastert "sent the message to people that if you're not loyal to the leadership, you may run into trouble. ... "