That should be a breeze — the real test was clearing the 60-vote hurdle today — and since the House approved fast-track last week, after balking the week before, the bill could land on the president’s desk for his signature by the end of the week.

True to form in a debate that’s packed in drama at every turn, the Senate vote on Tuesday was a nail-biter. The chamber initially approved the measure as part of a broader trade package back in May but with only two votes to spare. That meant the margin for error heading into the Tuesday vote was narrow. And it became razor-thin early Tuesday when Sen. Ted Cruz (R-Texas) — the Tea Party-courting presidential contender and an early backer of the handing Obama the extra negotiating room — announced he was switching sides and would be opposing fast-track. Cruz, in a Breitbart op-ed, cited deal-cutting between Republicans and Democrats since the Senate’s first vote in May as souring him on the initiative.

But a fragile agreement between Congressional Republican leaders and pro-trade Democrats about the path forward proved durable enough. After liberal House Democrats earlier this month voted down a measure extending assistance to workers displaced by globalization — a program they have traditionally championed but sunk as a procedural gambit to derail Obama’s trade push— GOP leaders decided to split fast-track authority apart and put it up for a separate vote.

The scheme would only work if Republicans convinced pro-trade Democrats that they would quickly follow the standalone fast-track vote with one on the worker assistance program, for which they’d also rally support. Senate Majority Leader Mitch McConnell (R-Ky.) further sweetened the deal by pairing the worker assistance with a program to help American steelmakers compete in international markets — an inducement for Rust Belt lawmakers in both parties wary of what previous trade deals have wrought. Despite threats from a number of the 14 Senate Democrats who helped lift fast track to passage back in May that they would flip against a so-called clean version, only one — Sen. Ben Cardin (D-Md.) — ended up switching sides on Tuesday.

After the vote, Sen. Ron Wyden (D-Ore.), the lead Democratic negotiator on trade as the ranking member on the Senate Finance panel, emphasized that work remains. “This is not about taking a victory lap,” he told reporters outside the Senate chamber, pointing to the need to ensure the other elements of the trade package follow fast track to passage. Highlighting the schism that the trade debate has opened within Democratic ranks, just steps away, a glum-looking Senate Minority Leader Harry Reid (D-Nev.) expressed his disappointment. “I still hate the whole program,” Reid said. “I’ve never voted for a trade deal, and I never considered voting for this one.”

Securing fast track does not guarantee passage of the deal itself, which links twelve Pacific Rim nations comprising 40 percent of global economic activity. But the authority would allow Obama to send his team of trade envoys back to the negotiating table with the assurance that whatever final deal they hammer out will get a simple up-or-down vote in Congress — a procedural streamlining that the administration views as critical to extracting the most favorable terms from their counterparts. Obama views the deal as the cornerstone of his second-term agenda, and it has spawned rare common cause between his White House and the corporate community, which has been marshaling against stiff and sustained opposition from labor and environmental groups to muscle fast track over the line.