In eight days, we should finally know which party will control the Senate for the new president’s term.

Oh, wait, just kidding. That battle could conceivably drag on for another year.

If Hillary Clinton and Sen. Tim Kaine (D-Va.) were to win the White House, it’s more likely than not that Democrats would win control of the Senate, too. But there’s a good chance that if that happened, they could hold a slim one-seat majority. And pretty much immediately after that, they’d have to defend Kaine’s open Senate seat, since his departure to 1600 Pennsylvania Ave. would set off a cascade of political dominoes in Virginia that could give Republicans another chance to take back control of the Senate.

Both sides would have to act quickly, since the battle for this Virginia Senate seat — and possibly the Senate — will take place over two expensive, high-profile races in two years.

Because this could all matter a lot in a few months, let’s run down how the political dominoes to replace Kaine could fall, in three steps:

1. 2016: The governor chooses who replaces him

Sometime after Election Day, Gov. Terry McAuliffe (D) will appoint someone to fill Kaine’s seat. Because McAuliffe is a Democrat, he’s going to appoint a Democrat (a fact that probably did not go unnoticed by Team Clinton when she picked Kaine). The Washington Post’s Virginia politics reporter, Jenna Portnoy, reports McAuliffe could go one of three routes:

  1. Appoint someone who promises not to run for office after the term ends in 2018, and put off this whole fight until then. But that means the Democratic candidate would lose the advantage of incumbency. So McAuliffe also could:
  2. Appoint someone who could make history, like the first black senator from Virginia since the 19th century. One of the favorites is Rep. Robert C. “Bobby” Scott (D) of the Richmond area. Portnoy reports that when McAuliffe walked into a labor conference in the summer, he was met with chants of “Bobby!” But Scott isn’t necessarily the best fundraiser, nor the most dynamic choice. So McAuliffe also could:
  3. Appoint a star fundraiser or more well-known figure. The options here are many (including the state’s other two Democratic members of Congress, Arlington-area Don Beyer and Gerald E. Connolly, as well as Attorney General Mark Herring). Portnoy goes into more details here.

2. 2017: Virginia voters get to choose

Either way, McAuliffe is going to appoint a Democrat. Which brings us to the next step in our process: A November 2017 special election, where Virginia voters would get to say who should replace Kaine. This is where things could get rough and tumble between Republicans and Democrats in Washington.

The Virginia Senate special election will be the only U.S. Senate race in 2017, and it could draw a lot of outside attention, especially if the national election seven days from now gives Democrats a slim, one-seat majority over Republicans. (It’s a distinct possibility: If Kaine is vice president, he’ll serve as the Senate president. So Democrats would need a net four seats to take back control of the Senate. They have a real chance in five to seven.)

The Virginia Democrat McAuliffe appoints will have the advantage of incumbency. But the dynamics of this special election could favor Republicans. And there are plenty of talented, well-connected Republicans who will jump at the chance for a rare opening in the U.S. Senate.

Among them is Rep. Barbara Comstock (R). Assuming she wins reelection to her Loudoun area congressional seat, she would probably love to avoid having to run a competitive race every two years. Portnoy reports that Carly Fiorina’s name is in the mix, too. And what about Ed Gillespie, the GOP strategist who almost unseated Sen. Mark R. Warner (D-Va.) in 2014? He’s running for governor, but there’s no reason he couldn’t switch over to this race. Oh and remember Rep. Dave Brat (R), the tea party star who ousted Eric Cantor in 2014?

If the fate of the Senate is at stake, there will be plenty of outside groups motivated and willing to help a Republican retake the Senate just a year after they lost it.

Plus, off-year elections tend to bring out more Republican voters (older, whiter, less transient).

So, no matter who McAuliffe appoints, it’s likely game-set-match for the winner of the November 2017 Virginia Senate seat.

3. 2018: Virginia voters get to choose (again)

Whoever wins the special election in November 2017 is going to have to turn right back around and do it all over again.

The election for the seat’s full, six-year term is in November 2018, which in election years is basically the next day. That means that in the middle of campaigning and raising tens of millions of dollars (again), this person is going to have to find time to actually do something in the slow-moving Senate to take back home and show for it.

Winning two big, statewide elections within 12 months is a hurdle that has felled many a politician. As The Post’s Portnoy notes, the last person to successfully do it was Harry Byrd Sr. (also a Virginian).

Here, the dynamics also slightly favor Republicans: The 2018 Senate map is the reverse of the 2016 one. Republicans are expected to be defending just eight seats, while Democrats will have at least 23 to worry about.

Whoever wants Kaine’s old seat is going to have to work hard for it. It’s entirely possible that if Democrats win the Senate Nov. 8, they will have to spend the next two years defending their Senate majority.

So, which party will have control of the Senate for most of the next president’s term? It's an answer we could have to wait more than a year for. Yay, politics.