Democrats had a really good night on Tuesday, easily claiming the Virginia and New Jersey gubernatorial races, flipping control of the Washington state Senate and possibly also the Virginia House of Delegates, passing a ballot measure in Maine that will expand Medicaid in the state, winning a variety of mayoral elections around the country, and gaining control of key county executive seats in suburban New York.

They also got pretty much exactly the results you’d expect when opposing a Republican president with a 38 percent approval rating.

That’s not to downplay Democrats’ accomplishments. Democrats’ results were consistent enough, and their margins were large enough, that Tuesday’s elections had a wave-like feel. That includes how they performed in Virginia, where Ralph Northam won by considerably more than polls projected. When almost all the toss-up races go a certain way, and when the party winning those toss-up races also accomplishes certain things that were thought to be extreme long shots (such as possibly winning the Virginia House of Delegates), it’s almost certainly a reflection of the national environment.

But we didn’t need Tuesday night to prove that the national environment was good for Democrats; there was plenty of evidence for it already. In no particular order of importance:

So while Northam’s 9-point margin of victory was a surprise based on the polls, which had projected him to win by roughly 3 points instead, it was right in line with what you might expect based on these “fundamental” factors. For instance, a simple model we developed based on the generic ballot and state partisanship forecasted a 9-point win for Democrats in Virginia and a 13-point win in New Jersey, pretty much matching their actual results in each state.

To put it another way, Tuesday’s results shouldn’t have exceeded your expectations for Democrats by all that much because you should have had high expectations already. Midterm elections — and usually also off-year and special elections — almost always go well for the opposition party, and they’re going to go especially well when the president has a sub-40 approval rating.

So, does that mean that Democrats are clear favorites to pick up the House next year? No, not necessarily. I’d say they’re favorites, but not particularly heavy ones. Democrats face one major disadvantage, and they have one major source of uncertainty.

The uncertainty is time: There’s still a year to go until the midterms. This could cut either way, of course. The political environment often deteriorates for the president’s party during his second year in office, and one can imagine a variety of factors (from attempting to pass an unpopular tax plan to ongoing bombshells in the Russia investigation) that could further worsen conditions for Republicans. One can also imagine a variety of factors that would help the GOP: Democrats overplaying their hand on impeachment; a rally-around-the-flag effect after a war or terror attack; Trump quitting Twitter. (OK, probably not that last one.) That Trump is so unpopular so soon in his term makes all of this harder to predict because there aren’t any good precedents for a president with such a poor approval rating so early on.

Democrats also face a big disadvantage in the way their voters are distributed across congressional districts, as a result of both gerrymandering and geographic self-sorting. Although these calculations can vary based on the incumbency advantage and other factors, my back-of-the-envelope math suggests that Democrats would only be about even-money to claim the House even if they won the popular vote for the House by 7 percentage points next year. The Republican ship is built to take on a lot of water, although it would almost certainly capsize if the Democratic advantage in the House popular vote stretched into the double digits, as it stands now in some congressional preference polls.

Nonetheless, my sense is that the conventional wisdom has, to this point, somewhat underrated the Democrats’ chances of having a wave election next year. And it’s for some fairly stupid (although understandable) reasons.

One is in the tendency to fight the last war. Journalists and pundits are always chastened by the “lessons” of the most recent election, especially if the outcome was surprising to them. And they usually like to argue that the results represented a realignment or a paradigm shift, rather than — as is more often the case — a fluctuation that came about from a combination of cyclical and circumstantial factors that may not replicate themselves. So they’re often slow to recognize signs that the political climate is shifting in the opposite direction from the supposed realignment, even when they’re really obvious. (Like, say, a Republican winning a Senate seat in Massachusetts only a year after the Democratic president took office.)

Second, the pundit class has a poor understanding of polling, and how it performed in 2016 — and it’s making 2018 punditry worse. As I wrote in our live blog on Tuesday night:

If you think numbers like Trump’s 37.6 percent approval rating are “fake news” because polls perpetually underrated Trump before, then the political climate doesn’t look quite as scary for the GOP. However, one needs to be careful about assuming the polling error always runs in the same direction; historically, it’s been just as likely to reverse itself from one election to the next. (For instance, polls lowballed Democrats in 2012 but then did the same to Republicans in 2014.)

Finally, there’s perhaps an unhealthy obsession with the white working-class vote, and its potential to sway the 2018 midterms in favor of Republicans. This could be more of a concern for Democrats in 2020. But the midterm electorate is typically more educated and better off financially than the presidential-year one. Also, most of the pickup opportunities that analysts envision for Democrats are in wealthy or at least middle-class areas. On average, the 61 Republican-held Congressional districts that the Cook Political Report rates as competitive rank in the 65th percentile in educational attainment (as measured by the share of adults with at least a bachelor’s degree) and also the 65th percentile in median household income. Some of them are fairly white, and some aren’t — but almost none are both white and working-class.

Competitive districts are mostly well-off and well-educated Demographic ranking for the 61 Republican-held Congressional districts that the Cook Political Report rates as competitive PERCENTILE RANK AMONG ALL 435 CONGRESSIONAL DISTRICTS SEAT ▲ ▼

COOK RATING ▲ ▼

EDUCATION ▲ ▼

INCOME ▲ ▼

NONWHITE ▲ ▼

Georgia 6 Leans Republican 99 92 62 California 45 Leans Republican 97 96 71 New Jersey 11 Leans Republican 96 99 36 Virginia 10 Toss-up 96 100 58 Illinois 6 Leans Republican 95 96 29 New Jersey 7 Leans Republican 95 99 43 Minnesota 3 Leans Republican 94 91 28 Texas 7 Leans Republican 94 80 77 Kansas 3 Leans Republican 93 81 39 Michigan 11 Toss-up 92 88 25 California 48 Toss-up 90 93 66 California 49 Toss-up 88 89 60 Pennsylvania 7 Leans Republican 88 92 18 Texas 32 Leans Republican 88 78 73 Pennsylvania 6 Leans Republican 87 90 19 Illinois 14 Likely Republican 86 94 28 California 39 Leans Republican 85 91 88 Colorado 6 Toss-up 85 85 57 Michigan 8 Leans Republican 82 71 22 Georgia 7 Likely Republican 81 82 76 Nebraska 2 Toss-up 81 66 37 Pennsylvania 8 Leans Republican 81 89 17 Virginia 7 Likely Republican 80 83 50 Minnesota 2 Toss-up 79 88 22 Florida 27 Leans Democratic 78 39 93 Pennsylvania 18 Likely Republican 74 67 2 North Carolina 2 Likely Republican 73 70 51 New York 11 Likely Republican 70 80 61 Virginia 2 Likely Republican 70 72 57 Arizona 2 Toss-up 68 25 58 New York 1 Likely Republican 68 94 33 New Jersey 3 Likely Republican 67 84 33 North Carolina 9 Likely Republican 66 50 60 Ohio 1 Likely Republican 66 49 45 Iowa 3 Leans Republican 64 65 18 Ohio 16 Likely Republican 64 68 3 Kentucky 6 Likely Republican 61 32 21 Montana Likely Republican 59 29 13 Florida 18 Likely Republican 57 47 48 New York 24 Likely Republican 56 51 21 Illinois 13 Likely Republican 55 27 26 Kansas 2 Leans Republican 50 38 19 New York 19 Toss-up 50 57 18 Washington 8 Toss-up 49 65 49 California 50 Likely Republican 47 81 68 Utah 4 Likely Republican 47 76 34 Virginia 5 Likely Republican 46 40 38 California 25 Toss-up 44 84 78 Florida 26 Leans Republican 42 45 95 Iowa 1 Toss-up 42 54 10 North Carolina 13 Likely Republican 41 21 53 New York 22 Leans Republican 37 42 12 New Jersey 2 Toss-up 36 60 52 Pennsylvania 16 Likely Republican 33 52 39 Michigan 7 Likely Republican 31 51 11 Illinois 12 Leans Republican 29 20 31 Maine 2 Leans Republican 24 18 <1 Texas 23 Leans Republican 18 35 91 New Mexico 2 Likely Republican 16 8 83 California 10 Leans Republican 5 58 77 California 21 Likely Republican <1 7 95 Sources: COOK POLITICAL REPORT, AMERICAN COMMUNITY SURVEY

Of course, this logic is somewhat circular: if Democrats aren’t trying to compete for the white working-class vote, outlets like Cook won’t list white working-class districts as being competitive. It’s possible there are some overlooked opportunities, such as in South Carolina’s 5th Congressional District, which Democrats came surprisingly close to winning in a special election earlier this year.

Nonetheless, Democrats have quite a few pathways toward winning the House that rely primarily on middle-class and upper-middle-class suburban districts, plus a few districts with growing nonwhite populations. Many of these are in coastal states or in blue states, including four of them in Virginia, four in New Jersey, four in Illinois, five in New York and eight in California, according to Cook’s list. It might not be advisable for Democrats to only target these sorts of districts; history suggests that parties usually benefit from competing ambitiously in all sorts of districts and seeing where the chips fall. But it’s plausible for them to do so and reclaim the House. Come 2020, though, it will be harder for Democrats to win back the Electoral College without rebounding among the white working class.

Last thing: while Tuesday’s results may not change the reality of the 2018 outlook all that much, it could change perceptions about it, and that could have some knock-on effects. (Politicians are often like “Morning Joe” panelists in how they think about elections.) Republicans’ retirement issues may get even worse; Democrats’ recruiting may get even better. Republicans might think twice about how they’re proceeding on tax reform — especially given that their current plans could have negative effects on just the sorts of wealthy coastal suburbs where Republicans performed poorly on Tuesday.

And there will be lots of recriminations about the race that Ed Gillespie ran in Virginia, which could change Republicans’ thinking on how they should relate to Trump. Some of this is going to be silly: Gillespie did no worse (and no better) than you’d expect given Trump’s approval rating and Virginia’s blue lean. But if those politicians think Tuesday was a huge game-changing deal, they may begin to act like it and create a self-fulfilling prophecy.