He is not alone in that reckoning, although many people in both parties declined to be quoted by name given the tenuous politics of the issue. Besides a new president, the Senate could have a new majority leader next year, Senator Charles E. Schumer of New York, if Democrats win control, and he is unlikely to promote an issue that so divides the union-friendly party.

“There is a pathway forward here,” Mr. Froman said. “And what we’re trying to do right now is just maximize the likelihood that we’ll be able to walk down that path successfully.”

Whether that is wishful thinking or a real prospect will have to come into focus well before November because supporters would likely need to begin congressional hearings in September to clear the path for a vote in the lame-duck session of Congress after Election Day.

And the forces do seem aligned against the pact’s approval.

Months ago, Senator Mitch McConnell of Kentucky, the majority leader who is pro-trade but worried about keeping Republican seats, ruled out a vote before the election. The so-called T.P.P. would phase out thousands of tariffs, open markets and impose new trade rules, including for labor rights and environmental standards, on signatory nations that span both sides of the Pacific, including Japan, Vietnam, Australia, Canada, Chile and Mexico.

And Mrs. Clinton appears to have put her finger on the scale against a vote in the lame-duck session. Asked by an anti-T.P.P. group if she would oppose a lame-duck vote on the accord if elected, Mrs. Clinton responded, “I have said I oppose the T.P.P. agreement — and that means before and after the election.”