With a government shutdown looming, Tuesday was set to be a day of bipartisan dealmaking between Democrats, Republicans and President Trump. By lunchtime, it was clear Tuesday was actually going to be a day of bipartisan blaming.

After Trump tweeted he didn't see a possible deal with Democrats, Democratic leaders backed out of a meeting with the president. Trump and Republicans are blaming Democrats for being “petty.”

As the day went on, it seemed as though the chance of a government shutdown — which budget experts put at 50/50 before all this — was creeping higher. Here's a breakdown of how the situation went from bad to worse:

9:17 a.m.: Trump tweets an attack on Democrats

It's a misleading tweet — House Minority Leader Nancy Pelosi (Calif.) and Senate Minority Leader Charles E. Schumer (N.Y.) don't want to raise taxes on Americans, for example — but the gist of it is that Democrats oppose the Republican tax bill and want to protect “dreamer” immigrants, so why should Trump trust them to negotiate in good faith?

How this exacerbates the potential for shutdown: The tweet seemed entirely directed at Trump's base. Seriously, Trump hit all the highlights with the right — crime, immigration, taxes.

The tweet was jarring to Democrats, given that Trump had briefly struck a nascent deal with them a few months ago to discuss protecting young undocumented immigrants. Now he's using that as a reason not to negotiate?

11:29 a.m.: Democrats pull out of the White House meeting over the tweet

“Rather than going to the White House for a show meeting that won’t result in an agreement,” Pelosi and Schumer said in a joint statement, “we’ve asked Leader McConnell and Speaker Ryan to meet this afternoon.”

Democrats, basically: Fine. You don't want to talk to us, we don't want to talk to you.

How this exacerbates the potential for a shutdown: There are policy chasms over immigration, spending levels, taxes and health care that Republicans and Democrats need to solve to avoid a shutdown. But they can't solve them if they're not talking to each other.

Last time congressional leaders met with Trump in budget negotiations, Trump abruptly sided with Democrats on a deal to extend a short-term budget and the debt ceiling for just a few months.

12:26 p.m.: Hill Republicans refuse to meet with Democrats alone

Republican leaders did not bite on Democrats' efforts to cut Trump out of the negotiations, even though privately, both sides agree that Trump's unpredictability seriously upends negotiations. You want to negotiate with us? Come to the White House, said Republican leaders in a statement to Democrats.

How this increases the risk for a shutdown: It officially cuts Democrats out of the negotiating process. And math alone says that could lead to a shutdown, since Republicans don't have enough votes to pass a spending bill on their own.

12:38 p.m.: White House calls Democrats petty, disappointing

In a statement, White House press secretary Sarah Huckabee Sanders called it disappointing that Schumer and Pelosi won't meet with Trump. The president’s invitation to Democrats “still stands, and he encourages them to put aside their pettiness, stop the political grandstanding, show up and get to work. These issues are too important.”

How this increases the potential for a shutdown: If Democrats weren't yet feeling insulted by the president, they are now.

2:30 p.m.: Senate Republicans make clear they have Trump's back

“It never occurred to me that I could just say to President Obama: 'I'm not showing up,' " McConnell said to reporters minutes after Trump lunched with Senate Republicans on Capitol Hill.

When reporters asked whether Trump's initial tweet was the trigger for all this, Sen. John Cornyn (R-Tex.) pivoted: “I assume as responsible adults that we're all responsible for our own behavior,” he said.

How this increases the potential for a shutdown: Behind the scenes, most Senate Republicans are just as sick of Trump as Democrats are. But if Democrats were hoping that would be enough to get Republicans on their side here, they were very mistaken.

2:45 p.m.: Senate Democrats thicken their hard line — and remind Republicans that a shutdown will happen on their watch

Next, it was Senate Democratic leadership's turn to get in front of the cameras and spin their side. Schumer reiterated that Democrats won't meet with Trump because of the tweet, which he said indicated that the president “isn't serious” about negotiating with them but is serious about scoring political points by dissing them.

“We're not going to sit down just for a photo op,” Schumer said.

He made one last pitch for Republicans to cut Trump out of the equation, reminding them how unpredictable the president is: “When the president stays out of it, we seem to do much better, the four leaders,” Schumer said.

How this increases the potential for a shutdown: Democrats have boxed themselves into a corner (well, they would argue Trump pushed them into a corner). The effect is they can't negotiate with Trump until he rescinds the tweet attacking them. But what happens next? Will they vote for a spending bill they don't like? Or will they vote against it and shut down the government?

As Schumer pointed out, any shutdown would happen while Republicans control all of Washington.

4 p.m.: Trump says Democrats will be blamed for a shutdown

Back at the White House, with empty seats beside him featuring name tags for Schumer and Pelosi, Trump addressed the media. “If that happens, we will absolutely blame the Democrats,” Trump said of a shutdown. “If it happens, it will be over illegals pouring into the country, crime pouring into the country, no border wall, which everyone wants. I got elected partially because of the border wall. We want stronger military funding. They don't.”

How this increases the potential for a shutdown: Trump's sticking on issues important to his base makes him less likely to compromise with Democrats, who want to advance polar opposite issues important to their base.