“The last thing the American people need right now is a massive tax increase, which would be a dangerous jolt to our economy,” Senate Minority Leader Mitch McConnell (R-Ky.) said in a statement. “Congress must pass a responsible fix to this middle class tax hike, the AMT; a fix that doesn’t replace one massive tax increase on Americans with another.”

Republicans plan to seize on a recent statement from Senate Majority Leader Harry Reid (D-Nev.) to embarrass Democrats for not acting more quickly on the AMT, according to one GOP Senate aide.

Reid told reporters last week that the Senate would not send the legislation to the White House before Thanksgiving, despite urgent warnings from the U.S. Treasury that delaying Senate action on the patch beyond the holiday could hold up the tax refunds of millions of taxpayers.

Senate Democrats are in a tough spot on the legislation, which they are under pressure to pass urgently without violating their vaunted pay-as-you-go budget rules. The AMT patch and a package of popular expiring tax breaks that the House passed on Friday will cost roughly $70 billion. Under pay-go, that tax relief must be accompanied by equivalent tax increases or spending cuts.     

Reid has vowed to adhere to the budget rules to patch the AMT. However, Senate Republicans, emboldened by a White House veto threat on the House-passed bill, are signaling they will balk at offsetting the cost of the patch. GOP aides claim the Republican conference is united enough to deprive Democrats of the 60 votes they need to pass the legislation through the narrowly-divided Senate.

In the House, Republicans were united in opposing the legislation, which they decried as swapping one tax increase for another. One Senate GOP leadership aide told The Hill on Friday that the House legislation was an “absolute non-starter” with Senate Republicans.

Complicating matters for Senate Democrats, there is no apparent consensus within the conference on the appropriate way to offset the tax relief, though most, if not all, Democrats appear to strongly prefer adhering to pay-go.

Several Democrats, including Sens. Charles Schumer (N.Y.) and John Kerry (Mass.), have criticized the House-passed measure raising taxes on private equity and hedge fund managers.

And Sen. Max Baucus (D-Mont.), the Finance Committee chairman, has expressed doubt about the measure’s viability in the Senate, yet has offered no other proposal to pay for the AMT patch.

On Thursday, Kerry told reporters that “there’s a lot of disagreement on what the offset should be,” adding that his preference is to repeal “the upper end of the Bush tax cuts” to pay for the patch.

Members of the Senate Republican leadership recently threatened to pursue a risky strategy if enough Democrats ultimately opt to waive pay-go to pass AMT relief. Sens. Trent Lott (R-Miss.) and John Kyl (R-Ariz.), the minority leader and GOP conference chairman, told The Hill that they might demand the extension of one or more of the Bush tax cuts in exchange for cooperating with Democrats on waiving pay-go. The Democrats would need 60 votes to override the rules.

Reid spokesman Jim Manley pounced on the strategy, saying that Democrats intended to patch the AMT this year and that Republicans were trying to hold them up.

“The reality is that Republicans are not only blocking attempts to provide AMT relief but, audaciously, many are demanding additional tax breaks for the wealthy as a price for passing AMT relief. This is cynical politics at its worst,” he said.

Republicans and Democrats both risk the fury of voters if they do not pass an AMT patch this year. Currently, only 4 million taxpayers pay the AMT, which Congress originally passed to ensure that the wealthy paid income taxes. But because the tax was never indexed to inflation, it is set to steadily swallow more and more middle-class victims. Unless Congress passes a patch, up to 25 million taxpayers could get hit by the tax next spring.

Manu Raju contributed to this report