Casey wrote Boehner a letter Monday saying he was "encouraged" by the speaker's remarks Sunday and called for a speedy vote on the legislation. It would slap a 30 percent tax on all future U.S. investments of former citizens deemed to have renounced for tax purposes, and bar them from ever setting foot in the country again.
"We must take action against those who capitalize on the advantages of United States Citizenship, but abuse the system to avoid paying their fair share," Casey wrote. "At this time, Washington needs to work together in a bipartisan manner. I request that you introduce the Ex-PATRIOT Act in the United States House of Representatives and call for an immediate vote on this important legislation."
Brian Fallon, a spokesman for Schumer, also prodded the nation's highest-ranked Republican.
"When even Speaker Boehner feels free to openly disagree with Grover Norquist, it is official that literally no one cares what Norquist thinks on this issue," Fallon told TPM in an email.
The Democrats' moves put Boehner in an all too familiar bind. If he comes out against the legislation he'll put Republicans on the wrong side of an issue that's easily exploitable by Democrats in an election year. But if he champions the bill he risks alienating the conservative base, which would loosen his already tenuous grasp on the speaker's gavel.
A spokesman for Boehner did not immediately respond to a request for comment. So far most Republican lawmakers have avoided discussing the legislation, but Democrats apparently intend to keep pushing until they take a firm stance.
"Honestly the speaker's words came to everyone as a surprise," said a Senate Democratic aide. "Everything from the other side of the aisle has been negative until Sunday. Perhaps his endorsement will bring more [Republicans] over."