President Obama has steadfastly refused to accept the notion he’s a lame duck — despite last year’s repudiation at the polls, which gave Republicans control of both houses of Congress.

Well, part of Congress seems fired up to make him a lame duck — by working to torpedo his hoped-for 12-nation trade deal.

It’s not the Republicans.

Nope: It’s Senate Democratic Leader Harry Reid lame-ducking the president — with New York’s own Chuck Schumer enthusiastically helping out.

On Tuesday, Reid declared he’s prepared to gum up the works to block debate on granting Obama “fast track” authority to negotiate the Trans-Pacific Partnership.

The senator had promised not to stand in the way of the TPP, which he opposes. But now he vows to block any progress until the Senate first votes on an infrastructure bill and an overhaul of the Patriot Act.

Reid plainly doesn’t care that a president of his own party wants the pact as a major legacy-builder. And Schumer is singing the same tune, dismissing trade deals as a “race to the bottom.”

His eye on succeeding Reid as the Senate Democrats’ leader, Schumer has plainly decided his president’s agenda doesn’t matter.

When Republicans pulled stunts like this, Reid and Schumer called them “obstructionists.” What’s the right term for Democrats blocking a Democratic president?