At 3:34 p.m., as Sen. Bob Menendez (D-N.J.) was just getting going with his speech against the House-passed Puerto Rico emergency bill, presidential contender Sen. Bernie Sanders of Vermont walked to his desk and asked for a question.

"It's a long question, but I certainly want my friend from New Jersey to respond," said Sanders. "Is this legislation smacking of the worst form of colonialism, in the sense that it takes away all of the important democratic rights of the American citizens of Puerto Rico? That basically, four Republicans who likely believe in strong austerity programs will essentially be running that island for the indefinite future?"

"Absolutely," said Menendez.

With that, Sanders had given his first remarks from the floor of the Senate in months — and from a familiar, embattled position. Even after losing Puerto Rico's presidential primary, Sanders has opposed the Puerto Rico Oversight, Management, and Economic Stability Act, usually referred to as PROMESA, calling it a shockingly undemocratic attempt to impose austerity measures on the debt-laden island. The bill would create an emergency board, dominated by Republicans, able to govern without accountability -- and to immediately lower the island's minimum wage.

As he straddles between his duties in the Senate and his ambitions as a presidential candidate, Sanders has repeatedly warned that PROMESA is unacceptable. "I'm going to vote against it, and I'm going to do everything I can to defeat a horrific bill," Sanders told reporters on the way into Tuesday's Democratic luncheon. Inside, according to several senators, Sanders made a case against PROMESA similar to the one he made on the floor.

But momentum is with the Republicans, and it's unclear if Sanders can even delay a final vote on the bill. The PROMESA saga has underscored how difficult it may be for Sanders to transfer the energy and attention of his presidential bid to the Senate, where Republican control ends most progressive causes before they can begin.

On June 9, two days after losing the last "Super Tuesday" primaries, Sanders attempted to stir the PROMESA debate by introducing his own Puerto Rico solution. The Puerto Rico Humanitarian Relief and Reconstruction Act, if passed, would have directed the Federal Reserve to provide "emergency financing to Puerto Rico to facilitate an orderly restructuring of the debt held by Puerto Rico." It was an echo of the quantitative easing used to inject capital during the first years of the post-2008 economic crisis, but framed as a pure issue of human rights.

It went nowhere. No one cosponsored the legislation. In the interviews he gave between June 9 and today, the subject of Puerto Rico never came up. The same was true in the speeches he gave, including highly-watched addresses to supporters on June 16 and June 23.

Sanders struggled to face two foes: Republicans, and the clock. By general agreement, any Puerto Rico bill had to be passed by July 1, or there would be fallout from lawsuits from the creditors expecting to be paid. Sanders pointed out that Republicans were responding to a crisis with austerity measures, and argued that so-called vulture funds had forced that crisis by buying up cheap Puerto Rican debt.

Skeptical Democrats worried that doing nothing would force more pain on the island, while the vulture funds collected money anyway. And other skeptics worried that Sanders's bill, if well-intentioned, would amount to a giveaway to those creditors. The choices seemed to be Puerto Rico defaulting on debt, hedge funds being bailed out, or austerity that at least cut back on how much the creditors would get for their meddling.

"They're terrible options, but I'm taking the one that least benefits the hedge funds," said Sen. Bill Nelson (D-Fla.), whose state has seen a surge of Puerto Rican immigration over the last decade. "If you do nothing, what money is left on the table — the hedge funds come in and grab it, leaving nothing for essential services."

With that attitude running through Sanders's caucus, and with Puerto Rico generally out of the news, Sanders did not rally his base or donor list. His Tuesday colloquy with Menendez lasted just 10 minutes, and did not mention his alternative bill, though a spokesman suggested he might add that as an amendment to PROMESA.

The problem: No one could say if Republicans would allow such an amendment. In lieu of something to rally people around, Sanders would oppose the bill.

"This will be taking away, perhaps, basic needs from hungry kids, in order to maintain what seems to me an unhealthy bureaucracy," said Sanders on the Senate floor, 10 minutes after he started talking. Shortly thereafter, he was gone, as Menendez kept up his speech.