Millions of votes are yet to be counted in the midterm elections, but early projections indicate that the Republican Party is on course to back control of the US House of Representatives for the first time in four years.

The upper chamber of Congress, the Senate, remains too close to call.

In the 100-seat Senate, only 35 seats are up for election this year, and there are only a handful of closely contested races. A net change of one seat toward the Republicans would give them control.

After two years of unified Democratic control in Washington, the power dynamic in the nation’s capital is poised to shift. Here are four very real implications for American politics for the next two years.

In their two years in office, Joe Biden and the Democrats were able to enact a fairly substantive agenda, which included massive spending on the environment, healthcare and other social programmes.

That would all end with a Republican victory.

There’s the chance of some co-operation – for instance, Republicans and Democrats did join together to pass gun control and technology investment this year and infrastructure spending last year. However, big-ticket liberal priorities on abortion, education and voting rights will be dead in the water.

Republicans have their own agenda, focused on border security, law enforcement spending, budget cuts and fossil fuel extraction. But even if the Republicans take both chambers of Congress, Democrats will be able block passage in the Senate using the filibuster rule, or in the White House using Mr Biden’s veto power.

For the next two years, legislative gridlock will be the name of game.

For two years, Democrats have been calling the shots – that’s meant an expansive investigation into the 6 January, 2021, attack on the US Capitol, and hearings on subjects including abortion, healthcare and voting rights.

If Republicans take control of congressional committees, the priorities will rapidly shift.

House conservatives have already promised a hearing into Joe Biden’s son Hunter’s business ties to China. They also want to look into the Biden administration’s immigration policies, the US withdrawal from Afghanistan and the origins of the coronavirus pandemic in China.

The Senate Judiciary Committee handles review of presidential nominations to the federal courts. For the past two years, Democrats have set a modern record for the number of new judges seated to lifetime appointments.

If Republicans also take control of the US Senate, expect the process for confirming Mr Biden’s nominees to come to a standstill. And if a Supreme Court vacancy opens up, there’s a good chance it could remain unfilled until the next presidential election.

With Democratic control of Congress, the US had a two-year reprieve from the game of chicken that have led to government shutdowns and near default on the national debt. That’s about to end.

Some Republicans, including Congressman Kevin McCarthy who is poised to become House speaker if Republicans take the chamber, are already threatening to force Democrats to agree to sweeping budget cuts.

The US has never defaulted on its debt. However partial government shutdowns due to the inability of Congress to approve annual spending legislation have become more common. It happened twice during the Trump administration and once under President Barack Obama.

If Republicans and Democrats can’t agree on a basic framework for government spending, another government shutdown by the end of next year seems highly probable.

Republican control of Congress would be a bitter pill for Mr Biden to swallow. He campaigned as someone who could unite Americans after a turbulent four years with Mr Trump as president.

Instead he will face a nation as divided as ever, a hostile Congress, and the possibility that Mr Trump himself will seek to win back the White House.

Most presidents suffer through electoral setbacks halfway through their first term in office. Although some have bounced back to win re-election, losing Congress will be seen as a sign of Mr Biden’s continued political weakness. It could renew calls for him to step aside for another Democrat when the 2024 presidential campaign season begins.

The president and his advisers all insist he will seek re-election. The White House has already announced Mr Biden will give a public speech addressing the election results on Wednesday.

How he handles that speech, and how he deals with the adversity that is coming in the months ahead, will go a long way toward determining how much support he will have in his own party for another four years in office.