WASHINGTON - Not to be outdone by their liberal counterparts, conservatives are working themselves into a state of dismay over what they disparagingly call "The Obama Compromise" tax bill.

Some key conservative activists and consultants claim that the bill could fail in the House because of growing grassroots opposition among Tea Party types - the mirror opposite of last week's Democratic concern about liberals torpedoing the same legislation.

"The sand is shifting under this very fast," said Craig Shirley, a Washington consultant who advises the Tea Party Patriots among other groups. "If it doesn't get voted on soon, it could get voted down."

That's probably an exaggeration. It's hard to imagine the GOP as a whole voting down a bill with close to $1 trillion in tax cuts. But it is growing more obvious by the minute that Republican leaders underestimated the internal political risks of the deal.

And if the discontent is deep enough, President Obama and the Republican leadership may wind up in the odd, even humiliating situation of depending on Democratic votes to pass what is essentially a Republican tax measure.

The grassroots GOP complaints are many and varied.

"We don't like the process that produced this," said Mark Meckler, a founder and leader of the Tea Party Patriot group. "It was put together in secret and in the dead of night, and the whole Tea Party movement is about trying to stop that kind of thing."

The would-be presidential candidates are noticing -- and responding. Eager to curry favor with the anti-establishment right wing in his own party, and eager to show his supply-side businessman bona fides, former Massachusetts Gov. Mitt Romney came out against the deal today in an op-ed piece in USA Today. His main objection: that the tax cuts would only last for two years, not enough time, he said, to lure companies into making the kind of long-range investments that create lots of jobs.

Rush Limbaugh and Sarah Palin oppose the deal, arguing that the GOP can get a better one once they take control of the House in January, and focusing on the fact that the deal does nothing to rein in runaway federal spending. "The answer to concerns like these is to cut spending," said Shirley, "and the bill doesn't address it."

Tea Party types are furious at the GOP leadership, including both Sen. Mitch McConnell and Speaker-to-be John Boehner, for setting what they regard as an accommodating tone even before the GOP takeover.

According to Shirley, they were also angered by the decision of the incoming House GOP leadership to award key committee chairmanships to two men regarded as products of the old, big-spending and big-government wing of the Republican Party: Rep. Fred Upton of Michigan, who was chosen to head the Commerce Committee, and Rep. Hal Rodgers of Kentucky, who will head Appropriations.

"The Tea Partiers are furious that these old-guard guys will be in there," said Shirley, "and they are showing their anger by going after the tax bill."

Conservative Republicans regard some of the "tax" related items in the bill as little more than wasteful spending - especially new or renewed subsidies for wind and solar power and corn-based ethanol.

These items were included in the Senate bill to help grease its passage there. But the result may be to have given the GOP backbenchers an excuse to vote "no" on the amended bill in the House.

The bill is turning into one of the early lines of demarcation in the 2012 field.

Some would-be presidential candidates are supporting the deal - and some may end up regretting their quick, early decision to do so. One of them might be former GOP Speaker Newt Gingrich, who came out in favor of the deal shortly after it was announced, perhaps out of collegial affinity with the next GOP Speaker.

But Gingrich is privately expressing growing concern about the measure.

Rep. Mike Pence is against.

Two former governors, Mike Huckabee and Tim Pawlenty, have also endorsed the deal, as has Sen. John Thune, who is a junior member of the GOP Senate leadership team run by McConnnell.