Democrats capitalized on President Donald Trump’s unpopularity in suburban districts to capture the House majority, but the president helped turn out Republican voters in states he won two years ago to add to the GOP’s Senate majority.

Democrats needed to win a net of 23 House seats to gain control, and as of early Wednesday, they had won 27. Of the 21 House races still undecided, Republicans are leading in 13 and Democrats are leading in eight.

Republicans headed into Election Day with 51 Senate seats. Sen. Dean Heller, R-Nev., lost his re-election, but the GOP defeated Democrat incumbents in Indiana, Missouri and North Dakota. Republican candidates lead as of Wednesday morning in too-close-to-call Arizona and Florida. It’s possible Republicans could have as many as 54 Senate seats in 2019, the most since 2005.

So what does all this mean? Here are three things to know:

1. Gridlock is back.

Divided government occasionally yields major compromises. But both parties are so polarized, it’s difficult to see traction on big-ticket legislation.

Trump has signaled a willingness to do a deal on infrastructure and lowering prescription drug prices, two issues House Democrats have said would be a priority in 2019. Trump reiterated the offers at bipartisanship at a day-after news conference Wednesday.

But would Democrats be willing to give Trump big policy victories in advance of his 2020 re-election? And do so at the same time Democrats are investigating Trump and papering the White House with subpoenas?

2. Oversight, oversight, oversight.

There’s another reason that Trump-Democrat deals may not happen: House Democrats are preparing to go into overdrive on oversight in 2019, focusing on both the Trump administration and the private sector. Beginning in January, Democrats will have subpoena power to compel document production and testimony from company executives.

From Trump’s tax returns and business dealings to his 2016 Russia connections, Cabinet scandals and policies such as separating immigrant families at the U.S.-Mexican border, Democrats will be investigating every inch of the Trump administration. It’s already a troubled relationship that will grow only more poisonous as the investigations intensify, making bipartisan deals on big-ticket items unlikely.

3. Debt ceiling, budget caps.

Unless Congress acts during the lame-duck session of Republicans’ final days in charge, the White House, House Democrats and Senate Republicans will have to agree in early 2019 on raising the $21 trillion debt ceiling before the March 1 deadline. Lawmakers will also have to act before next fall to address sequestration budget caps scheduled to snap back in fiscal 2020.

In the past, these issues have been fraught with budget brinkmanship and threats of default, as each party tries to jockey for concessions from the other side.

The most likely outcome in 2019 is a return to gridlock. But the must-pass legislation on the debt ceiling and budget sequestration could become vehicles to carry other, unrelated provisions if bipartisanship breaks out.