What if Republicans have an epic wipe-out in November's midterm elections?

All the evidence points to a disastrous GOP belly flop. We know that the party that holds the White House typically loses seats in Congress during a midterm election. That would be the case even if President Trump were popular. But he isn't. True, he was doing notably worse a year ago, with his approval ratings hovering between 36 and 38 percent. For the past three months he's bounced around in a narrow range of 41 to 43 percent. That's an improvement — but it's still historically low. And when it's combined with his consistently very high disapproval rating, we're left with a president regularly and significantly underwater by anywhere from 9 to 20 points. And this is the case in the midst of a boom economy, with unemployment near historic lows and growth relatively robust.

Despite the strong economy, Democrats have consistently led in congressional generic ballot polls for more than a year. RealClearPolitics' polling average puts the spread at about 7 points. At no point in the last year has RCP had Republicans getting any closer than 3.2 points.

It's true that Trump does remain extremely popular among the roughly 24 percent of Americans who are self-described Republicans. But this, too, could hurt Republicans in November. Trump's in-party popularity keeps the GOP's elected officials and candidates for office rallying around the president in multiple ways — mimicking his blatant racism and cruelty, his support for far-right policies (including trade wars and immigration restrictionism), his vicious partisanship, his hostility to the Mueller investigation, his attacks on "fake news" and the press as the "enemy of the people," and even his bizarre fondness for Russia and Vladimir Putin in the face of overwhelming evidence that Putin's government interfered in the 2016 election. These might be acceptable, and even necessary, positions for a Republican to take in 2018. But they're unlikely to endear Republican candidates to independent voters, and they may well be enough to motivate Democrats to show up to vote en masse against the president and his morally compromised party.

The evidence that this is precisely what's happening is right there in front of us, in a series of elections over the past 18 months — special elections to fill vacated House seats, statewide elections, local elections. Over and over again, at all of these levels, Democrats have outperformed expectations, often winning in districts that in recent election cycles have strongly favored Republicans. That's because Democrats are energized, highly motivated to push back hard against the president and what the GOP has become since Trump stormed the stage during the 2016 Republican primaries.

That energy and motivation isn't likely to wane. It has already persisted since Trump's victory nearly two years ago. And the very things Trump does to keep his own base motivated — the rallies, the appalling viciousness of the ICE raids and detentions and family separations, the racist denigration of immensely popular sports figures — also keep Democrats motivated. That's the double-edged sword of negative partisanship.

Democrats are likely to do very well in November — with their floor at the present sitting just below what it would take to capture a House majority, and the upper end giving them a majority with a substantial margin. (The odds of them taking the Senate are longer, but far short of impossible.)

If the Democrats do take the House, that would not only give them a foolproof way to block Trump's legislative agenda (beyond even what the GOP House majority has managed to achieve all by itself, through a mixture of dysfunction and dissension). Winning a majority of House seats would also give the Democrats subpoena power, which would enable an aggressive investigation of the Trump administration's unprecedented graft and myriad other forms of corruption. And it would empower the Democrats to impeach the president — though conviction (requiring a two-thirds vote in the Senate) would remain exceedingly unlikely, no matter what Special Counsel Robert Mueller turns up.

That would herald a nearly two-year period in which Trump would (presumably) be heading toward a bid for re-election while feeling cornered by his political enemies and tempted at every turn to gin up the enthusiasm of his base. Which would, once again, keep him protected from members of his own party. But it would also keep the Democrats invigorated.

It's far too early (nearly two years from knowing for sure who the Democratic nominee will be) to predict how such a campaign would unfold. But it is nonetheless possible to make an informed prediction that it will pit a Democrat who is at least not wildly unpopular (that is, someone other than Hillary Clinton) against a bitter and angry Trump who lashes out constantly against not only his opponent but also against any and every prominent American who dares to express criticism of him. It's also likely that Trump will threaten, as he obliquely did in 2016, not to accept, in the event of a loss, the results of the "rigged" election.

I can't think of anything more poisonous — or more likely to prompt historically high levels of turnout on the part of all Americans who reject Trump's tyrannical ambitions. These voters would turn up at the polls in an effort to repudiate these ambitions so overwhelmingly that there can be no denying the decisiveness of the outcome.

Is that our future? It's far too soon to know with certainty. All we can say at the moment is that three months out from the midterm elections of 2018, the state of play is exactly what one would expect to see in the early stages of the unfolding of precisely such a scenario.