The House is expected to approve major food safety legislation today. Though many on Capitol Hill pronounced the bill dead last week, the measure bounced back to life over the weekend when the Senate unanimously–and quite unexpectedly– advanced the beleaguered bill late Sunday night.

The FDA Food Safety Modernization Act, which would, for the first time in several decades, update the U.S. Food and Drug Administration’s oversight over the food supply, has been in legislative limbo for over a year.  As dean of the House, Rep. John Dingell, D-MI, who has worked on the food safety law for many years, put it:  “This legislation has seen more procedural fits and starts than any other.”

The legislation survived a near-fatal constitutional snafu, filibuster threats, fierce debate over controversial amendments, and managed to gain ground amidst a jam-packed legislative agenda in one of the most productive Congresses in recent history.

Consumer advocates, industry groups, and public health experts–who have all followed the ups and downs of the bill with bated breath–responded enthusiastically as the bill sailed through the Senate, again. But, as NPR’s April Fulton noted on Sunday: “No one’s exactly popping champagne corks yet. There’s always the potential for another oops.”

“There shouldn’t be any obstacles but this is one bill where it is not over until it is over,” said Jean Halloran, food safety director at Consumers Union, which publishes Consumer Reports, in an email response to Food Safety News.  “However, we are optimistic.”

Sandra Eskin, director of the food safety campaign at the Pew Charitable Trusts, echoed the same cautious optimism in an email: “We hope that the bill will pass the House sometime [Tuesday.] We understand from House Leadership that they are doing everything they can to speed this vote through.”

The bill is not expected to have trouble clearing the House.  A stronger version of the legislation cleared the lower chamber in July 2009, with a bipartisan 283-142 vote.  Earlier this month, the House approved an identical version, which was attached to a large all-encompassing continuing resolution to keep the government funded through September, 212-206, with 35 Democrats joining Republicans to vote against it.  The bill must be re-approved by the House because it’s no longer riding the spending bill–the CR died in the Senate.

It is not clear how leadership in the Senate came to a deal to advance the food safety legislation as a stand-alone bill.  For months, leadership had to circumvent Sen. Tom Coburn’s, R-OK, vehement opposition to the measure in order to advance the bill.  Coburn threatened to filibuster the bill over the cost–approximately $1.4 billion over five years–though the Congressional Budget Office says the provision is deficit-neutral.

Less than 48 hours before the bill passed the Senate unanimously, Coburn’s office told Food Safety News that the senator would oppose the “so-called food safety bill” if it were attached to a continuing resolution.  After the Senate cleared the bill via unanimous consent Sunday, Sen. Coburn’s office did not return a request for comment.

Slate’s David Weigel reported Sunday that he talked to several staff members of senators who had voted against the bill the last time around–before the constitutional error was realized.

“Nobody knew why their bosses had let it sail through,” said Weigel. “The best theory I’ve heard is that key Republicans, having seen the bill pass with supermajority support (73-25), and having become satisfied that there were no back-door nanny provisions in the bill, decided that it wasn’t worth keeping the Senate in session past Christmas to debate it.  It’s a Christmas miracle, if the key characteristics of Christmas are self-interest and fatigue.”

President Obama is expected to sign the bill before Christmas.