George Bush earned the win he needed and expected in the Iowa caucuses but now faces a much tougher challenge--a two-front war--in New Hampshire, Republican leaders and consultants said last night.

With two social conservative challengers, publisher Steve Forbes and talk show host Alan Keyes, running stronger than expected in Iowa, Bush will be under pressure from the right, even as he tries to turn back the challenge of Arizona Sen. John McCain, the maverick reformer who tops most New Hampshire polls.

With the voting in the leadoff primary a week away now, McCain led Bush by 3 to 6 points in most of the recent polls. The senator made an early decision not to campaign actively in Iowa--and paid the price. His fifth-place showing in Iowa was described by Eddie Mahe, a veteran Republican consultant with no candidate affiliation, as one "that may take some of the wind out of McCain's sails."

But several other observers said whatever embarrassment McCain may suffer at beating only his colleague, Utah Sen. Orrin G. Hatch, is more than offset by the strategic advantage he may gain from having both Forbes and Keyes shooting at Bush from the opposite flank of the party.

One McCain adviser, noting that those two candidates drew roughly 40 percent of the votes in Iowa, said, "If they do half that well in New Hampshire, it will be tough for Bush to win." His assumption--widely shared by neutral observers--is that most of the social conservative votes would otherwise go to Bush, rather than to McCain, whose positions on campaign finance and other issues have been criticized by antiabortion leaders.

Linda DiVall, a pollster who worked for Elizabeth Dole before she left the race, said the Iowa results create "an almost perfect situation for McCain" in New Hampshire. "It's a test for Bush to see if he can fight a two-front war," she said.

Bush pronounced himself "thrilled with a record-setting victory" that saw him capture more than four out of every 10 votes--leading the field among most demographic groups and doing particularly well among older and wealthier voters and those who said they were looking for a strong leader. He did significantly better than he had done last August when Iowa Republicans conducted their straw poll. Then Bush led Forbes, 31 to 21 percent, with Dole taking third.

Still, Mahe called Bush's margin a "so-what" win--not small enough to damage his standing in the race but also not enough to give him a boost in New Hampshire.

David Keene, head of the American Conservative Union and a veteran of many past presidential campaigns, said Bush "hit his performance target." But he added that Forbes's showing may persuade many conservatives "to stay with him at least for another round or two. It makes it harder for Bush to attract the votes he needs to put McCain away."

Forbes, who poured millions of dollars of his own money into organizing Iowa, found his strongest support among those who gave priority to his signature issues of taxes and abortion.

Forbes has not been a notable factor in New Hampshire until this point, drawing support from only about one voter in eight in recent polls. But he has been endorsed by the Manchester Union-Leader, the state's largest newspaper, and observers said that if he could find a way to exploit the tax and abortion issues, he might make an impact. His campaign manager, Bill Dal Col, publicly predicted that McCain and Forbes would push Bush into third place in New Hampshire--a forecast that most others consider brash. Keyes, the former diplomat who emerged in the GOP debates as the strongest voice condemning the "moral decline" of the nation, was described by almost everyone as having done exceptionally well in Iowa, where another conservative activist, Gary Bauer, had outdistanced him in the straw poll.

Keyes is expected to join Forbes in pressing Bush on the abortion issue--a subject the Texas governor has no wish to see front and center in the campaign. But there was no certainty any of the top three Iowa finishers will get much of a "bounce" out of Iowa.

Dan Schnur, the McCain campaign communications director, said yesterday afternoon that "unless the results are extraordinary one way or another, they probably won't change the landscape in New Hampshire at all." Another observer, who has run past GOP presidential campaigns, said, "Bush won. Three days from now, that's all that people will remember about Iowa."

While some candidates have parlayed a second-place showing in Iowa into a burst of energy and votes in New Hampshire--as Gary Hart did in his 1984 Democratic race with Walter F. Mondale--more often than not the two states have behaved independently of each other.

In 1996, for example, Robert J. Dole defeated Patrick J. Buchanan and others in Iowa, but Buchanan reversed the result in New Hampshire. In 1980, George H.W. Bush, father of the current candidate, upset Ronald Reagan in Iowa, but Reagan turned the tables on him in New Hampshire.

What makes the Iowa bounce even more problematical this year is that the surviving candidates in both parties are scheduled to participate in a pair of debates Wednesday evening on WMUR-TV in Manchester, the state's biggest television station. The results of those debates, which are expected to draw the largest audience of the campaign, could well have a more significant influence on undecided or wavering New Hampshire voters than any impressions the Iowa results create in their minds.

"On Tuesday, everyone will be talking about Iowa," Schnur said, "but by Wednesday, the conversation will be about the upcoming debate. And from Thursday on, it will be the debate dynamic that is important."

A Bush strategist, while not dismissing the importance of the debate, expressed confidence that "winning Iowa will reinforce Republican voters' belief that Bush is the strongest candidate in this field."

Bush's finishing first with religious conservatives in Iowa, his strategist said, "will make it harder for anyone like Forbes to attack his conservative credentials. And it also would augur well for us in South Carolina," whose Feb. 19 primary also is likely to be heavily affected by the religious right. McCain has based his long-shot hopes on upsetting Bush in both New Hampshire and South Carolina. Having Forbes appear as a strong competitor on Bush's conservative flank in those two states would probably improve McCain's chances of springing a surprise.