Washington (CNN)President Barack Obama's free trade initiative has cleared a major procedural hurdle in the Senate, despite two days of behind-the-scenes wrangling forced by his own party.
President Barack Obama's trade bill advances in Senate
The House, though, looks like a much tougher challenge.
The Senate cleared its 60-vote threshold Thursday to advance "trade promotion authority" legislation and start debate — which greases the wheels for the 12-country Trans-Pacific Partnership by guaranteeing that Congress won't try to amend the deal.
The vote undid a stinging rebuke that Democrats delivered Obama on Tuesday, when even members who support free trade voted against the bill, demanding a series of trade-related concessions. Obama met with some of those Democrats on Tuesday night, and the White House released their names after the meeting, putting additional pressure on those senators to support Obama in Thursday's vote.
The debate and amendments are expected to play out over several days, but now that Democrats have convinced Senate Majority Leader Mitch McConnell, R-Kentucky, to allow votes on several other worker protection and trade preferences programs, the bill appears on course to clear the Senate.
It will then move to the House, where Republican Speaker John Boehner and his leadership team have strongly backed the legislation — but they're facing dissent from tea partiers within their own ranks.
The debate there will put on display an odd populist alliance: Labor unions and environmental groups that fear the damage expanded trade could cause are joining ranks with isolationists and Obama's fiercest critics on the right, who distrust the President and are loathe to hand him any extra power.
Those groups both argue, for very different reasons, that TPP will ultimately prove harmful.
House Democrats meanwhile rallied behind Minority Leader Nancy Pelosi of California in railing against the trade deal, and it's not clear whether the White House has broken off party members in significant numbers to buck House leadership and support Obama.
Pelosi floated chopping the length of the trade promotion authority the bill would give Obama from six years down to three with reporters on Thursday.
"While three years in the trade promotion authority bill may be appropriate for foreseeable trade agreements, there is unease with a process that would provide carte blanche for agreements unknown, for countries to be determined, for a time in perpetuity," she said.
The pro-trade Democratic votes would likely come from the moderate New Democrat Coalition.
House Republican leaders say they know their caucus will splinter, so they'll need at least some Democratic votes to give Obama the trade authority he wants.