Everything seemed to be going so smoothly just after Labor Day. President Trump tweeted favorably about dealing with "Chuck and Nancy," and the two Democrats returned the favor.

"He likes us. He likes me anyway," Senate Minority Leader Charles E. Schumer (D-N.Y.) said in mid-September. He was caught on a live microphone on the Senate floor explaining to another senator how he and House Minority Leader Nancy Pelosi (D-Calif.) reached a pair of major fiscal deals with Trump.

By Tuesday, every last ounce of goodwill had been drained out of the Donald-Chuck-Nancy partnership. The implosion left the fate of funding for the Pentagon and domestic federal agencies up in the air heading into the holiday season. Perhaps more important, it seemed to poison the well for reauthorizing a children's health program and resolving the fate of hundreds of thousands of undocumented immigrants who were brought into the country when they were children.

It also served as the latest lesson in what it is like to negotiate with a president whose dealmaking experience came in the real estate world, where he was known to back away from nearly cinched agreements as a ploy to leverage better deals.

Trump began the day by denouncing the Democrats, on Twitter, for wanting "illegal immigrants" in the country. He predicted that no deal would come together on a year-end package to fund the government and the other key issues.

Schumer and Pelosi then canceled plans to attend an afternoon meeting with Trump, House Speaker Paul D. Ryan (R-Wis.) and Senate Majority Leader Mitch McConnell (R-Ky.), fearing Trump no longer saw the huddle as a chance to map out final deals.

"We're not going to sit down just for a photo op. This is too serious," Schumer told reporters later. And Pelosi went to Twitter to express her dissent, intentionally using the president's social-media tone.

"[H]e's more interested in stunts than in addressing the needs of the American people," Pelosi tweeted. "Poor Ryan and McConnell relegated to props. Sad!"

It's a long way from where things stood in mid-September, after Trump acquiesced to the two Democratic leaders on a plan for short-term funding of the federal government and allowing the Treasury to increase its borrowing limits to finance the national debt.

The president also told the Democrats that he would support permanent legal status and eventually a path to citizenship for the "Dreamers," the young undocumented immigrants, in exchange for beefed-up funding for border security.

These talks floored Republicans. They wanted to work on a longer timeline on the fiscal disputes and were flummoxed when, after his harsh rhetoric on illegal immigration during his campaign, Trump sided with Democrats whom he had previously denounced as supporting "open borders."

Pelosi wanted clarity from Trump after he gave Congress six months to resolve the fate of the Dreamers or he would end the Deferred Action for Childhood Arrivals program, an Obama-era executive order halting deportations for those young undocumented immigrants. So she asked the president to tweet his support for no deportations during that period — and the tweet landed in the middle of a House Democratic caucus meeting.

"For all of those (DACA) that are concerned about your status during the 6 month period, you have nothing to worry about," Trump wrote.

Most Democrats encouraged their leaders to continue the talks, but they also expressed great concern about being set up for a double-cross. Particularly concerned were members of the Congressional Hispanic Caucus. They always feared that a man who began his campaign calling Mexicans "rapists" would not keep his word about signing legislation formalizing the DACA protections.

But Schumer maintained his optimism as bipartisan negotiations took place among congressional negotiators, suggesting this month that he had little fear of a partial federal government shutdown amid a standoff over immigration. "We won't come to that. I think we'll have Republicans joining us to support DACA," he said.

That optimism came crashing down Tuesday. "Chuck Schumer and Nancy Pelosi did not show up for our meeting today," Trump told reporters at the White House. "I'm not really that surprised. We have a lot of differences. They're weak on crime, they're weak on illegal immigration. They want the illegal folks to come pouring into our border."

So, what happened?

"The staffs were making great progress until the president stepped in. We were very close on a number of issues," Schumer told reporters. He said that Trump got in the way of what were "serious, mature negotiations" on a major piece of legislation.

Sen. Richard J. Durbin (D-Ill.) said that other Republicans had told him Trump was stunned by the negative reaction he got from the conservative base after he started wheeling and dealing with the Democratic leaders.

"And since then his whole rhetoric has changed," Durbin said.

Now it's unclear whether Trump wants to try to bring about a shutdown of the federal government — funding runs out Dec. 8 — in a bid to force congressional Democrats to back funding of the border wall that he has long supported.

That sort of confrontation, something that most of the public would despise, might be exactly the kind of fight that Trump's base wants. It is unclear whether Ryan and McConnell are prepared to jump into that abyss with the president, knowing that it is their members who are on the ballot in next year's midterm elections.

Schumer always saw this coming. In his hot-mic moment in mid-September, he told his colleague that he had warned Trump about going to the "far right."

"If you have to step just in one direction, you're boxed. He gets that," Schumer said.

In a whisper, Schumer even predicted his new negotiating partner might transform Congress. "Oh, it's going to work out, and he'll make us more productive, too," he said.

That prediction remains very much in doubt.

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