Try not to smile too hard as identity politics devours its practitioners.

Last night, Mary Katharine performed an astute roundup of the series of harsh recriminations being slung at Democrats by Democrats amid an internecine fight over a proposed free trade deal with a variety of Asian nations. Last night, the U.S. Senate failed to pass a bill that would have provided the president with the authority he needed to enact the Trans-Pacific Partnership trade agreement largely due to Democratic obstruction.

For weeks, President Barack Obama has singled out one of the deal’s most vocal opponents, liberal icon Sen. Elizabeth Warren (D-MA), for criticism over her recalcitrant resistance to this deal. In retrospect, it was probably inevitable that her supporters would accuse the president of bitter and latent prejudice against women. The left would like you to believe that the only reason anyone could oppose their peculiar policy prescriptions is unthinking and brutish bigotry. That unseemly debating tactic had previously been reserved for Republicans, but now Democrats are getting a taste of their own medicine.

Yesterday, progressive Sen. Sherrod Brown (D-OH) determined that Barack Obama was indulging in a bit of anti-women bias by having the temerity to criticize Warren. She is, after all, a woman, and for Obama to treat her the same way he would a man in her position is horribly discriminatory… That’s how that works, right?

“I’m not going to get into more details,” Brown said after criticizing the president for being “disrespectful” to Warren and making his frustrations with her “more personal than he needed to.”

“I think referring to her as first name, when he might not have done that for a male senator, perhaps?” the senator asked pointedly. “I’ve said enough.”

Indeed, he had. Just hours after Brown sent up this smoke signal, National Organization for Women president Terry O’Neill took the senator’s logic to its ultimate conclusion. “Yes, I think it is sexist,” O’Neill said of Obama’s criticisms of Warren. “I think the president was trying to build up his own trustworthiness on this issue by convincing us that Senator Warren’s concerns are not to be taken seriously. But he did it in a sexist way.”

The White House, filled to the brim as it is with progressives, knows how to play the identity politics game as well as anyone else. White House Press Sec. Josh Earnest did not dismiss the insult to the president’s character and insisted that Brown should “find a way to apologize” for his remarks.

“Sen. Brown is a standup guy, and I’m confident after he’s had a chance to look at the comments he made yesterday that he’ll find a way to apologize,” Earnest told the hosts of MSNBC’s Morning Joe.

Brown has so far balked at offering any mea culpas, but he will probably be compelled to issue a dishonest apology for disingenuously accusing the president of misogyny. Of course, the president will pretend to accept the insincere apology, and we will all dance the night away as this exhaustingly fraudulent pageant continues according to the script.

But this sideshow cannot mask the disaster that this trade spat has created for Democrats. Politico’s Manu Raju detailed the scope of the damage done to the president’s stature by this rebuke from the members of his own party.

For months, the Senate seemed to be a sure bet for Obama’s trade agenda. More than a dozen Democrats were prepared to buck progressive hard-liners and give the White House a big bipartisan victory.

The breakdown that occurred Tuesday underscored the failure of the White House to keep a lid on mounting tensions with its own party. It highlighted the White House’s reluctance to stand behind a Senate Democratic leadership team eager to embrace hardball tactics to stymie the GOP agenda and force more concessions before moving forward on the trade bill. It showcased the influence of Ohio Sen. Sherrod Brown, whom Reid, the minority leader, relied on to help solidify opposition in the Senate Democratic Caucus.

And it laid bare the growing rift between Democrats who believed Obama went too far in picking a fight with the liberal icon Elizabeth Warren — and others in the Senate Democratic Caucus who are frustrated with the freshman senator’s uncompromising approach on trade and other issues.

A president who spent months after the 2014 midterm rout his party suffered casting himself as freshly emboldened is today well and truly a lame duck. It wasn’t Republicans or American voters who imposed this condition on the president, but the members of his own party. This was the most unkindest cut of all.