The Food Safety bill was supposed to be a lame duck session triumph for the Democrats, an important piece of legislation that had passed with bipartisan support. But, as it turns out, there’s just one catch: the legislation was unconstitutional. It instituted new taxes — which the Constitution only allows the House to do. From Roll Call:

By pre-empting the House’s tax-writing authority, Senate Democrats appear to have touched off a power struggle with members of their own party in the House. The Senate passed the bill Tuesday, sending it to the House, but House Democrats are expected to use a procedure known as “blue slipping” to block the bill, according to House and Senate GOP aides. …
Senate Majority Leader Harry Reid (D-Nev.) could simply drop the issue and let the next session of Congress start from scratch, a strategy that would allow him time in the lame-duck session to tackle other last-minute priorities …
Or he could try to force the issue in the Senate after the House passes a new version of the bill. But in order to do that and still tackle the other issues, he would need a unanimous consent agreement to limit debate.
According to Senate GOP aides, a unanimous consent agreement is all but certain to be a nonstarter because the bill’s chief opponent, Sen. Tom Coburn (R-Okla.), will not agree to such a deal.