The Republican Party was offered a choice today between two sharply different versions of conservatism as Texas Gov. George W. Bush and Arizona Sen. John McCain intensified their debate over the bedrock GOP issue--tax cuts.

The competing visions echoed long-standing divisions within the party between advocates of deep cuts in income tax rates and those who worry that such cuts could threaten the projected budget surplus and would do nothing to ease the long-term threat posed by a $5.6 trillion national debt.

It was McCain who made the case today that a smaller tax cut than advocated by Bush was the more conservative approach after sustained criticism from Bush that the Arizona senator had embraced an approach to taxes and budgets more in tune with Democrats than with Republicans.

In a speech to the Concord Chamber of Commerce exactly three weeks before the Feb. 1 New Hampshire presidential primary, McCain called on Republicans to adopt "a new fiscal conservatism for the next century" by using the growing federal budget surplus for a relatively modest tax cut and as an opportunity to shift their party back closer to its historic role as the guardian of fiscal responsibility.

McCain's appeal to history appeared to be a political bet that most Republicans no longer see major tax cuts as the surest way to economic prosperity and would prefer more emphasis on savings and investment to achieve that goal. It was also a departure from the Reagan-era orthodoxy embraced by most Republican presidential candidates that deep tax cuts are always optimal policy--and is one reason some party activists are distrustful of McCain.

As he outlined his plan today, McCain gave New Hampshire voters a clear-cut alternative to the more ambitious tax cuts promised by Bush: less in immediate tax relief, but with a promise of longer-term economic health by bolstering the Social Security and Medicare systems and by paying off a portion of the national debt.

The debate between the two presidential contenders represents a variation of the battles between GOP tax-cutters and budget hawks during the 1980s, when Republicans squabbled yearly over tax cuts versus deficits.

Marshall Wittmann of the Heritage Foundation and a McCain supporter argued today that the new debate revolves around tax cuts versus savings and investment. "I don't think it's supply-siders versus budget hawks, it's income versus wealth," he said.

Steve Moore of the Cato Institute praised McCain for proposing moves to privatize Social Security, but said the senator's tax cut plan was the weakest of any Republican running for president. "Only a very small percentage of the future surpluses would be devoted to tax cuts, so that's not the true Reaganesque approach to fiscal policy."

Greg Mueller, an adviser to GOP candidate Steve Forbes, called the McCain proposal "the Concord Coalition plan," a reference to an organization that is devoted to maintaining the budget surplus and reducing the national debt. Forbes has proposed a flat income tax, and his advisers estimated today that his proposals would cut $648 billion in taxes over five years, far more than either Bush or McCain.

Mueller said McCain's plan is "likely aimed at independent voters, which McCain is trying to consolidate to beat Bush in New Hampshire. . . . But even if it helps him in New Hampshire, it could be a political disaster in other GOP primary and caucus states, where a more conservative base shows up to vote."

In his speech, McCain, who is widely regarded as Bush's main challenger for the GOP presidential nomination, said that "it is the essence of true conservatism to be fiscally responsible. True conservatism both protects the interest of those who pay an overly heavy tax burden today, and those who are too young to pay taxes but not too young to be threatened by a potential future of a crushing debt of $5.6 trillion and a broken Social Security system."

McCain's plan would provide tax cuts totaling $237 billion over the next five years, less than half the $480 billion in tax cuts promised by Bush, who would lower tax rates across the board. Instead of deeper cuts, McCain said he would devote 62 percent of expected surpluses outside the Social Security program to shoring up the retirement system, 10 percent for Medicare and 5 percent to pay down the debt. The projected five-year debt repayment would total almost $59 billion, barely scratching the surface of the $5.6 trillion debt.

In recent days, McCain has been criticized for waging "class warfare" against Bush by contending that the Texan's tax plan would provide the most benefit to the wealthiest taxpayers. In unveiling his own plan today, McCain clearly sought to blunt such criticism and to prevent Bush from seizing the mantle as the true tax-cutting conservative in the race. Toward that end, McCain used the words "conservative" or "conservatism" 11 times in his speech today as he argued that his combination of a smaller tax cut, protecting Social Security and paying down the debt was the more conservative path that Republicans should follow.

Bush spokesman Ari Fleischer said that McCain is still "echoing Al Gore" by criticizing Bush's plan as too large. "People will pay more in taxes in a McCain administration than in a Bush administration, hardly a conservative notion," he said.

The outlines of the McCain plan were well known before today's speech. Some of its key components would expand the amount of income taxed at the lowest 15 percent rate from $43,050 to $70,000 for couples and from $25,750 to $35,000 for individual taxpayers; reduce the so-called "marriage penalty" by increasing the standard deduction for couples; double the child tax credit to $1,000; eliminate the earnings test that reduces benefits to some Social Security recipients who work; and eliminate income taxes for military personnel while they are stationed overseas.

In addition, McCain's plan would create a new savings vehicle, the Family Security Account, in which single taxpayers could contribute $3,000 and couples $6,000 a year. The contributions would be tax-deferred and the money could be withdrawn for any purpose after one year, when it would be taxed.

The success of McCain's tax cut plan would largely hinge on his ability to convince Congress to close dozens of corporate tax loopholes. McCain put out a four-page list of loopholes that he would target and his aides said they accounted for $151 billion, or 64 percent of the total $237 billion tax cut.

Staff writer Juliet Eilperin contributed to this report from Washington.