This is the fourth piece in a four-part series examining the dynamics of the new Congress. | Part one, Part two, Part three

For President Trump, the second half of his first term will be very different from his first. Since January 2017, he’s enjoyed a Republican majority in the House and the Senate that advanced his agenda, shielded him from investigations and largely refused to challenge him.

The ongoing government shutdown is the quintessential capstone on two years of congressional Republicans adhering to the demands of Trump and his base. Rather than bring up the Senate-passed clean funding bill and put the onus on Trump to sign it or veto it over his border wall money, House Republicans voted on a measure to keep the government running that included $5.7 billion for the border wall that Trump repeatedly said Mexico would pay for. House passage of that bill effectively ensured a government shutdown because it couldn’t pass the Senate.

Next week, Trump will no longer have House Republicans to do his bidding. For the first time he will experience divided government. For any president, the prospect of partisan oversight is nerve-racking, but for the Trump White House it’s especially perilous, given the array of issues the Democrats are eager to probe.

Is there any chance Trump will get along with the Democrats?

Here are a few reasons that’s highly unlikely. We already received a sneak peek into how negotiations between Trump and Democratic leaders will go when Trump invited Rep. Nancy Pelosi (D-Calif.) and Sen. Charles E. Schumer (D-N.Y.) to the Oval Office for an on-camera discussion about funding the government. It was pure political theater that degenerated very quickly. On Friday morning, Trump tweeted: “We will be forced to close the Southern Border entirely if the Obstructionist Democrats do not give us the money to finish the Wall."

Trump also warned after the Democrats won the House that if they launched investigations into him, he’d view that as an act of war. That won’t deter Democrats, who are eager to fire their opening salvos.

And, finally, there’s no incentive for Democrats to compromise with Trump, or vice versa. In this political climate, purity overrides compromise. To be seen working with Trump will not help Democrats going into the 2020 presidential and congressional elections, at least during the primaries.

What will Trump’s relationship be like with Republicans?

For Trump, there’s good and bad news here. Many of the GOP lawmakers who challenged him, in rhetoric if not in action, resigned, retired or lost their seats, leaving behind mostly those who align with the president. But Trump’s recent decision to unilaterally pull troops out of Syria has angered many Republican lawmakers, including those who have been his close allies on Capitol Hill like Sen. Lindsey O. Graham (S.C.). Foreign policy could complicate Trump’s relationship with his party.

Mitt Romney’s arrival to the Senate as Utah’s freshman senator will be interesting to watch. Extremely critical of Trump in the past, he could assume the role of elder statesman and be the party’s conscience. But during his campaign he walked back some of his dissent, so he could also choose to keep a low profile and not take up that mantle.

Will Trump’s behavior change with this new dynamic?

Trump is lucky it’s the House and not the Senate that flipped because he’ll still be able to get his nominees for key administration and judicial posts confirmed. So he’s assured some victories.

The Senate can also save Trump from being removed from office if the House moves forward with impeachment charges.

Which brings us to the big outlier: special counsel Robert S. Mueller III’s report. If his findings implicate Trump, the president will need every friend he has in Congress to stand by him, which could get increasingly difficult for GOP lawmakers. Mueller will dictate so much of what happens next year, including Trump’s temperament.