Republicans seem to have held on, barely, to a US House seat near Columbus, Ohio, that they have occupied continuously since 1983.

That outcome doesn’t tell us much new, but it reinforces some conclusions we already had reasons to reach.

First: Democrats are enthusiastic about voting. There’s a temptation to treat their turnout purely as a function of their hostility to the way President Trump has conducted himself in office. But it’s important to remember that partisans of the opposition party are typically more motivated to vote in midterm elections than supporters of a president — any president. Grievance is a more powerful motivator than satisfaction.

Trump has, however, probably angered Democratic voters more than another Republican president would’ve done. He may also be changing the mix of voters in each party.

Some upper-middle-class suburban voters who backed Mitt Romney over Barack Obama in 2012 voted for Hillary Clinton over Trump in 2016. They seem to be voting for Democrats this year, too. They may want to send a message to the Republicans about their support for Trump, or they may be on the way to long-term alienation from the GOP.

Either way, the result was that the Democratic candidate in Ohio won a much higher percentage of Clinton voters than the Republican candidate won of Trump voters. That’s why the race was so close.

Second: What might be called the Republican-establishment message isn’t generating countervailing enthusiasm within the Trump coalition. Congressional Republicans would in general like the election to be about the strong economy and the alleged role their tax cut played in creating it. They’d rather not have it be about an unpopular president.

But Trump’s political instincts might be better than theirs. Gratitude for the tax cuts doesn’t seem to be bringing Republicans to the polls. It’s probably even less helpful in getting those white working-class voters who backed both Obama and Trump to side with GOP candidates for Congress. (Obama/Trump voters outnumbered Romney/Clinton voters nationally, although in many congressional districts the reverse was true.)

Again, grievance may do more to move voters. To the extent that it’s working-class voters Republicans need, those grievances are likely to be more cultural than economic. The typical Republican message on economics tends to leave those voters cold, and most Republicans are too ambivalent and cross-pressured to adopt Trump’s protectionist economics wholeheartedly.

But a Trumpish cultural message — illegal immigrants are a threat to the country, and the Democrats and the media treat you as a bigot for wanting to defend it; the elites are going after your president because they hate you — could blunt the Democratic advantage on enthusiasm.

Republicans don’t need to endorse every Trump tweet or initiative to pursue this strategy. They’ll probably not want to defend the administration’s family-separation policy, for example, and instead talk about the new left-wing campaign to abolish the agency that enforces immigration laws.

Third: Democrats may be on firmer ground talking about economics while Republicans raise cultural issues. I admit I’m biased on this point: I’ve long written that economic issues tend to help Democrats and cultural ones to help Republicans. So I may be looking for reasons to confirm a pre-existing belief.

But the dynamics of these midterms are offering such reasons. If liberals and Romney/Clinton voters are already enthusiastic about supporting Democrats this fall, and Republicans are likely to use cultural issues to gin up their own votes, it might make sense for Democratic candidates to spend most of their time talking about economic issues. Portraying the Republicans as self-dealing plutocrats could keep Democrats’ existing voters while making it harder for Republicans to get their sometime-allies in the white working class to show up.

One difficulty for Democrats in pursuing this strategy is that cable-news networks, even if they’re broadcasting an anti-Trump message, are drawn toward the cultural rather than the economic issues. Democratic politicians would have to try to pull the discussion in a different direction.

Which side is successful in determining what the elections are about will go a long way to determining who wins them.

© 2018, Bloomberg Opinion