A GOP group is putting Republican lawmakers "on notice," threatening to campaign against anyone who breaks ranks to vote for the more than $800 billion economic recovery package. 

The National Republican Trust PAC put out a statement Tuesday claiming it would provide financial support for primary challengers to any stimulus-supporting Republican in the next election. 

"Republican Senators are on notice," the group's director Scott Wheeler said in a statement. "If they support the stimulus package we will make sure every voter in their state knows how they tried to further bankrupt voters in an already bad economy." 

The release did not name names, but was obviously directed at the three Republican senators who joined Democrats to advance the Senate version of the bill Monday. 

Republicans Sens. Arlen Specter of Pennsylvania, and Olympia Snowe and Susan Collins, both from Maine, are expected to vote for the bill Tuesday. Specter is up for re-election next year and Snowe in 2012. Collins was re-elected in 2008 and won't be up again until 2014.

Republican Senate leadership continues to speak out against the bill, a blend of spending and tax cuts which they say is too costly and contains too much wasteful funding. House Republicans unanimously opposed the House version two weeks ago. 

But Specter told FOX News Tuesday that Congress must take action "promptly and decisively" to prevent "catastrophe." President Obama gave a similar warning in his prime-time press conference Monday. 

"This legislation is a bitter pill to swallow," Specter said. "But we're facing a situation where the current economic problems could turn into another depression like 1929."