House Republicans facing a tough vote on the American International Group bonus tax appear to be hardening their opposition, with Democrats getting ready to charge them with protecting the firm’s executives and considering whether to stay in Friday to force the issue.

House Minority Leader John Boehner (R-Ohio) announced he is voting against the bonus tax plan, as have many other Republicans.

“This bill is nothing more than an attempt for everybody to cover their butt up here on Capitol Hill. It’s full of loopholes. A lot of these people who are getting these bonuses likely live in London — it’s not clear how raising this tax is going to recover that money. The fact is the Treasury secretary can recover all this money, and he can do it immediately,— Boehner told reporters Thursday. “And that’s what the bill we wanted to vote on today would do. It would require the Treasury secretary to submit a plan in 14 days to recover all the money.—

Either way, Republicans are in a tenuous position. If they vote for the bill, many will be violating pledges not to vote for tax increases. If they vote against it, they risk headlines saying Republicans are blocking punishment against AIG derivatives traders.

Several Republicans said they were planning to vote against the bill, arguing it is an unconstitutional “bill of attainder— because it singles out a small group of people for punishment.

“I’m voting no,’— House Republican Policy Committee Chairman Thaddeus McCotter (R-Mich.) said. “I took an oath to uphold the Constitution.—

McCotter said Democrats voted to protect AIG bonuses, and “now they are putting up this fig leaf.—

“It is patently unconstitutional,— added Rep. Mike Simpson (R-Idaho), who hadn’t decided yet how he will vote. “We’re singling out somebody for a tax increase.—

But Simpson said it was a tough vote because of the anger at AIG. “I’m as upset about these bonuses as anybody out there,— he said.

Simpson said he didn’t think the legislation would ultimately become law but was an effort to show outrage. And Simpson slammed Democrats for putting it on the suspension calendar, saying they were trying to put Republicans in a tough spot. Because the bill is on suspension, which requires a two-thirds vote, the bill’s fate is effectively in the GOP’s hands.

Rep. John Campbell (R-Calif.) said the ends don’t justify the means.

“The means are really scary. … I absolutely despise the precedent of using the tax code for punishment,— he argued.

Campbell said Democrats were trying to “cover their ass. It’s that simple.—

Other GOP Members, however, said they were leaning toward supporting the bill.

Democrats, meanwhile, were mulling whether to stay in Friday to force the bill through if Republicans bring the bill down this afternoon. “It’s possible,— said a House Democratic aide.