With a new poll every day showing John McCain tied or leading among likely New Hampshire primary voters, Texas Gov. George W. Bush abandoned any pretense of above-the-fray campaigning today and charged his rival with offering a Potemkin tax cut and lacking command of crucial issues.

What a difference a new year makes. At the end of the last year, Bush was extolling the Arizona senator's virtues, refusing to challenge him even on policy matters. "He's a good man," Bush said repeatedly, turning up his Texas twang. "I like him a lot."

This year finds Bush still making similar statements--while at the same time comparing McCain to Al Gore and Bill Bradley. That is, of course, a not so subtle way of saying: "Hey, John: You're a liberal."

Today, he continued his attack on McCain's $237 billion tax plan, which is about half of Bush's proposed $483 billion cut. "We have a difference of opinion on who to trust, Washington or the taxpayers," Bush told reporters this morning in Pittsfield, N.H. Later, Bush likened McCain's assertions that Bush's tax cut gives too much to the rich and would endanger Social Security and Medicare to "what I would expect from a Vice President Gore or a Senator Bradley."

McCain brushed off Bush's latest criticism. "Governor Bush has made three or four charges about my tax plan that have proven to be false and I'm sure this will be, too," he said after a town meeting in East Greenwich, R.I., this afternoon. "But there are provisions that we will cut out as far as corporate welfare and corporate benefits are concerned that someone may not like--that's what the special interest business is all about."

McCain pointed to polls showing that most Republicans prefer his plan to Bush's, which McCain advisers call "the blank-check tax cut."

McCain and Bush have been going at it over taxes since the beginning of the year. But their debate took on an even sharper tone today as the Bush campaign sought to characterize McCain as a flip-flopper who lacks a cohesive domestic policy agenda and comes to the table unprepared with facts and figures to back up his proposals.

"I think it's a Washington mind-set that says I'll lay something out and then if it takes on a little water, I'll amend it and keep amending it," said Bush. "I believe that someone running for president must lay out a plan that he is willing to defend from the minute it's laid out."

Bush aides point to McCain's initial lack of a response to Bush's assertion that McCain's tax plan would pose a $40 billion tax increase on working Americans by repealing certain tax exemptions for employer-provided benefits.

McCain says the real figure is $4 billion and would not affect employees, but only corporations, which would no longer be able to receive a tax benefit for providing such perks as sports tickets and spa memberships. Child care and education subsidies are exempted in McCain's proposal, so corporations could still deduct those costs from salaries when figuring payroll taxes.

Tom Rath, a Bush adviser and GOP state committeeman here, said: "This is at least the third time [McCain] has put this plan out there and then changed it. Look, you've got to be able to play at this level."

The Bush campaign, believing it has a potent political hammer to bludgeon McCain with, took to the television airwaves today with a new ad featuring Bush saying: "My opponent trusts the people of Washington to spend money. I trust the people of New Hampshire to make the right decisions for their families. If he says something I don't agree with, I am going to point it out. I darn sure don't agree with saying you're going to take $40 billion of employer-related benefits and have people pay taxes on them."

McCain tried to squeeze Bush on the tax issue by signing a pledge to oppose any sales tax on goods sold over the Internet, which is now precluded by a temporary moratorium passed by Congress. "I challenge all the candidates, including Governor Bush, to take this same pledge," McCain said as he signed a blown-up version of the pledge at a breakfast of the Greater Nashua Chamber of Commerce.

Bush said he favors the moratorium, but wants more study before it is made permanent. McCain's political consultant Mike Murphy held court at the back of the room, declaring that Bush's position "looks to me like a huge, billion-dollar tax increase."

Aboard his bus, McCain refused to elaborate on the ramifications for state governments of a ban, which would permanently preclude them from collecting taxes on Internet sales. "It would be a permanent ban on Internet taxes," McCain said. "I cannot elaborate."

Allen reported from Nashua.

CAPTION: Republican presidential candidate George W. Bush speaks at a stop in Pittsfield, N.H., where he dropped his above-the-fray stance and compared GOP rival John McCain to the Democratic front-runners.