Will Republicans continue to have sole control of the federal government next year, or will Democrats win a house of Congress — and gain the ability to check President Trump’s power?

And will Republicans continue to have a massive advantage in state governments in 2019, or will Democrats make major gains — including in offices that will be crucial for the next redistricting?

The big-picture consequences of the midterms can be difficult to wrap your mind around. There are 435 House seats, 35 Senate races, 36 governorships, 6,066 or so state legislative seats, dozens of referenda, and many more state and local offices on the ballot this November. And between federal and state races, the potential ramifications are quite different.

Federally, it’s all about whether a house of Congress will flip — or whether President Trump and Republicans will continue to have total control over legislation, investigations, and nominations.

Few matters are more important to a presidency than which party controls Congress. Presidents Bill Clinton, George W. Bush, and Barack Obama all began their first term with their allies controlling both houses. But they all eventually lost both, and their presidencies were enormously constrained afterward — as would be the case for Trump.

In a divided Congress, a president’s party can no longer pass new laws with their votes alone. The opposition to the president gains subpoena power, which they can use for rigorous investigations. And should the Senate in particular flip, Trump would be enormously constrained in whom he can get confirmed for the Supreme Court, lower courts, his Cabinet, and other offices.

Meanwhile, in many states, Democrats have the chance to gain the power to actually implement their own affirmative agendas. To the extent that the “blue wave” materializes, the balance of power in American politics will shift in concrete ways — the consequences of which will ripple outward, in potential new policies, laws, and cultural shifts. If Republicans manage to mostly hold on, though, the current status quo will remain.

The national stakes: checking Trump’s power with legislation, investigations, and nominations

If Democrats win back either house of Congress, unified Republican control of Washington will end, with major ramifications.

1) Legislation: Currently, Republicans can use the special budget reconciliation process to send sweeping new legislation to President Trump’s desk with only GOP votes. (This is in contrast to most bills, which need 60 votes to beat a Senate filibuster.)

Trump’s GOP successfully passed a major tax cut bill with budget reconciliation and tried hard to repeal Obamacare with it too (though they ended up failing). And if Republicans hold on to Congress, they could well make another similar play in 2019 — either for Obamacare repeal, more tax cuts, or major cuts to Medicare, Social Security, food stamps, or welfare (as some conservatives have proposed).

But if Democrats win either the House or the Senate, this will come to an end: The conservative legislative agenda will be dead. Instead of a friendly Congress working to pass Republican bills, Trump will have to spar with Democratic majorities. The result will likely be gridlock (though unusual bipartisan compromises are possible, depending on the issue).

2) Investigations: Winning control of the House or Senate wouldn’t just give Democrats veto power over new bills. It would also give them subpoena power — which would let them investigate the Trump administration far more aggressively.

House and Senate committees can send subpoenas for documents and can compel witnesses to come in and testify. However, those committees are controlled by the majority party. So over the past two years, Republicans have been calling the shots — deciding when to investigate closely, and when to look the other way. (Some key GOP committee chairs have used their power to try to cover for Trump on the Russia scandal.)

Democrats, meanwhile, would be eager to investigate a whole host of things should they regain subpoena power. There’s the Russia scandal, but there’s also Trump’s businesses, a host of questionable administration policies and scandals, or even the sexual assault allegations against Trump. (And remember — Hillary Clinton’s email use first came under scrutiny because of House Republicans’ investigation into the Benghazi attacks.)

3) Nominations: Finally, should Democrats retake the Senate, President Trump would immediately become seriously constrained with regards to getting nominees confirmed.

Currently, Senate Republicans can confirm any Trump appointee with a simple majority, and they don’t need any Democratic votes. So they’ve been working closely with the White House on this project — particularly when it comes to confirming judicial appointees who will serve for life.

All that would change under a Democratic Senate. Majority Leader Chuck Schumer would decide on the calendar for considering and confirming nominees — which would let him bury many of Trump’s picks indefinitely. This would be most important should a new vacancy arise in the Supreme Court (or should Anthony Kennedy’s seat remain vacant). Democrats would also be able to stop Trump from appointing sycophants to key federal law enforcement posts or other powerful Cabinet positions.

The stakes in the states: control of state governments, ballot initiatives, and control of redistricting

But for Democrats to actually get the power to affirmatively do something of their own — rather than to just block or gain negotiating leverage over President Trump — they have to look to the states.

1) Control of state governments: The Democratic Party’s performance in state elections under Barack Obama was positively dismal. Currently, the GOP controls 33 out of 50 governorships and 67 out of 99 state legislative chambers. And Democrats have full control of just right out of 50 state governments (compared to the GOP’s 26, with the remaining ones being split between the parties).

But most of these state offices are on the ballot in 2018 — giving Democrats an opportunity to either gain full control of or make inroads in states that have been dominated by Republicans for years.

Full control would give Democrats the chance to pass a host of new liberal policies into law. Take New Jersey. Democrat Phil Murphy replaced Republican Chris Christie as governor this January, which finally gave the party full control of state government. Since then, Democrats have passed equal pay and paid sick leave legislation, raised taxes on people making more than $5 million a year, passed an automatic voter registration law, set new renewable energy requirements (that also subsidized nuclear power), restricted gun magazine capacity to 10 rounds, and reworked school funding to steer more toward needier districts.

And even gaining partial control of a Republican-dominated state — the governorship, the state House, or state Senate — would have a similar effect, for Democrats, of winning a house of Congress. It would bring the conservative legislative agenda to a halt.

2) Ballot initiatives: Then in some states, major, important changes won’t even have to wait for a new government to be sworn in — because voters will get to directly approve or reject them on the November ballot.

Daniel Nichanian has a great roundup of this year’s key referenda, which include Medicaid expansion in three red states, potential restoration of voting rights to felons in Florida, redistricting reform in Michigan, automatic voter registration in Nevada, minimum wage increases in Arkansas and Missouri, and marijuana legalization in Michigan, among others.

3) Control of redistricting: Finally, the once-a-decade redistricting process is scheduled to kick off in 2021 — but many of the politicians who will actually be involved in redrawing state lines will be elected next month. (These are mainly governors and state legislators.)

I’ve written on this at more length here, but it’s one of the most neglected stakes of the 2018 midterms. Republicans utterly dominated the redistricting process last time around, and as a result, the House of Representatives map gives them a major built-in advantage, as do several state legislature maps.

The best chance Democrats have of turning this around is by winning key governor and state legislative races so they’ll get to draw the lines — or at least ensure themselves a seat at the table with Republicans — in 2021. Conversely, if Democrats fumble this opportunity, Republicans will get the chance to lock in, and even perhaps increase, their built-in advantages in maps across the country. It’s not just the future of the Trump administration on the line this fall — it’s the next decade of American politics.