Sen. Claire McCaskill, center, talks to Joe Maggio at an American Legion post in Independence, Mo., in August. (Christopher Smith for the Washington Post)

It’s hard to recall midterms that were as highly anticipated and potentially critical to the future of both parties as the 2018 elections. At stake in 2018 are not merely the majorities in the House and Senate but also the identity of the GOP — and whether there will even be a single GOP. The Democratic Party’s direction for 2020 and beyond may also be dramatically affected by the 2018 results.

Consider the unique circumstances that are converging. The president is under investigation by a special counsel. The GOP has majorities in both houses but so far shows no inclination to oust its president, no matter how unpopular he may be with the electorate at large. A change in control of the House likely will be the difference between impeachment and no impeachment.

Stephen K. Bannon, the president’s ally and soulmate, is preparing primary challenges to traditional Republican candidates by alt-right, pro-Trump types. We have never seen a president, even indirectly, try to savage his own party. The result could be a collapse of the alt-right; a collapse of traditional Republicans; or a weakened GOP that allows for Democratic majorities in one or both houses. (Hey, if Roy Moore can win in Alabama, why couldn’t any wacky alt-right candidate win a GOP nomination — and then get wiped out in the general election? A recent poll has Moore ahead of incumbent Luther Strange by 14 points but only 4 points ahead of Democratic nominee Doug Jones.)

The GOP numbers could be reduced in one or both houses, but as is often the case, we could see a disproportionate number of moderate members lose. The rump group that remains may be more in the sway of the alt-right. Combine the Bannon-vs.-establishment dynamic and a possible downturn in the economy, a devastating report by the special counsel and/or a real international crisis, and the GOP could suffer devastating losses.

If the House and/or Senate majorities vanish, it’s not clear that Republicans will blame Bannon, let alone President Trump. It will be the media’s fault or the establishment Republicans’ doing, according to Trumpkins, and it will be the Trumpkins’ fault, according to the traditional Republicans. If things are tense now when Trump meets with the Senate majority leader and the House speaker, just wait until Sen. Mitch McConnell (R-Ky.) and Rep. Paul Ryan (R-Wis.) are minority party leaders.

From there, the possibilities spin out in a slew of different directions:

  • The Trumpkins leave the GOP, and Trump runs as a third-party candidate.
  • The GOP establishment panics, revolts and mounts a serious primary challenge for the control of the party in 2020. If Trump prevails, he keeps the GOP and the others walk.
  • Trump welcomes the Democratic majorities, who will make deals with a president ready to concede anything and everything. The GOP as a party cannot hold together under those circumstances. Multiple factions could break apart.

The scenarios are endless and wildly disparate. But all those outcomes assume that 2018 is rather disastrous for the GOP.

What if, instead, the economy keeps humming along, the special counsel comes back with a nothing-burger report and the presence of so many competent generals or ex-military advisers keeps Trump from going off the deep end in international affairs? Maybe the GOP narrowly holds the House and picks up Senate seats. Then the Democrats are in for a world of hurt as the far left and the moderate factions of the Democratic Party blame one another and initiate a brutal civil war that makes the contest between Bernie Sanders and Hillary Clinton look like a love-fest. Can they coexist, or will one side or another take its marbles and go home?

Dizzy yet? You’re not alone. All of this leaves us with a few conclusions.

First, no one can be sure where American politics is headed; we may be in for remarkable continuity or an entirely different landscape. We tend to assume that the future will be just like the present, with two parties — a right-leaning one and a left-leaning one. But history is a guide to the future until it is not. Multiple parties? New parties? We should rule nothing in nor out.

Second, in a time of political turbulence, we can see chaos, gridlock and hyper-partisanship — but also opportunity. If ever one wanted to challenge someone in a supposedly “safe” seat or declare an independent candidacy, 2018 would certainly be the time. A personality or a brash idea can make a difference when the sides get scrambled and both traditional parties run extremist nuts.

Third, moderates in both parties have a lot to learn from one another. Democrats know that plutocratic tax and economic policy is a dead-bang loser. Republicans know that an election without an overarching vision (rather than a grab bag of micro-issues for each constituency) is essential. If not collaboration, we may see some convergence on some issues — with the Trump and Sanders factions left out in the cold. In a post-2018 environment, thoughtful R’s and D’s should be open, even eager to explore cross-party alliances on a temporary, issue-by-issue basis or as a long-term political movement. They’d be wise to spend time getting to know each other. If their respective parties descend into extremism, chaos or both, they’ll need one another like never before.