All right, all right, I didn’t see the wave coming. All those margin-of-error polls seemed to suggest that Democrats would likely hold their own — probably not keep the Senate but make a respectable showing overall. Wrong.

All the caveats are true. It was a midterm, when the incumbent president’s party usually gets a comeuppance. The Senate losses were within historical norms. In other races, some of the high-profile Republican victories involved incumbents who managed to survive after the scare of their political lives, such as Govs. Rick Scott of Florida, Scott Walker of Wisconsin and Sam Brownback of Kansas.

But no, this turned out to be a genuine wave — one with serious implications for 2016 and beyond.

You’re telling me that Anthony Brown, an uncontroversial if unexciting candidate, couldn’t win the governor’s race in Maryland, usually a Democratic fortress? That Sen. Mark Udall couldn’t squeak to re-election in Colorado, a state that has seemed to be trending blue? That Sen. Kay Hagan of North Carolina could run what the political cognoscenti called a nearly flawless campaign and still lose? That Sen. Mark Warner of Virginia, who had been expected to win his race easily, managed to survive — pending a final vote count — only by the grace of a few precincts in the Washington, D.C., suburbs?

Democrats may be tempted to say relax, we’ve got this. Voter turnout was low even for a midterm. Two years from now, we’ll have a presidential election — the Democratic Party knows how to win those, having taken the popular vote in five of the last six — and the Senate seats at risks will mostly be GOP-held.

This kind of magical thinking would be a terrible mistake.

It is true, as I have noted many times, that history and demography are on the Democrats’ side. But no one should assume that the party can automatically re-create the coalitions — women, minorities, young people — that swept Barack Obama to victory in 2008 and 2012. It’s not as easy as the Obama campaigns made it look.

Getting these people to the polls requires more than a high-tech system to identify, target and nag them. It requires compelling candidates and compelling ideas. If Democrats have either, this would be a good time to bring them out.

Politicians such as Obama do not come along every day. His personal story, rhetorical skill and easy charisma allowed him to inspire listeners — to make them dream, hope and dare to imagine a better world. More important, he made them want to vote.

When African-Americans, Latinos, students, single women and other Democratic constituencies go to the polls in large numbers, the party wins. They generally stayed home Tuesday, however, and there is no guarantee that they will turn out in 2016. The Republican Party’s older, whiter constituency, by contrast, votes pretty much like clockwork.

The Democratic midterm campaign generally consisted of targeted appeals to these constituencies. African-Americans were asked to support the nation’s first black president and his agenda. Latinos were asked to be patient and wait for immigration reform, which they would never get from the GOP. Women were asked to be frightened of what Republicans might do to restrict their reproductive rights. Udall so built his losing campaign around “war on women” issues that he was ridiculed as “Senator Uterus.”

Maybe this was the best Democrats could do, given Obama’s current unpopularity and the country’s sour mood. But there was nothing hopeful or aspirational about the party’s message. Democrats gave their voters plenty to worry about but nothing to believe in.

Republicans, it should be noted, were even more negative and less aspirational. They offered voters basically one thing only: a chance to inflict Obama and his party with a loss. There was no hopeful vision of a better future. But the GOP did display a kind of energy and drive that few Democratic candidates were able to match.

Republicans increased their majority in the House and tightened their grip on statehouses nationwide. They appear to have gained ground in the use of state-of-the-art campaign technology.

Tuesday’s returns will be interpreted, reinterpreted and overinterpreted. Might Democrats make too much of this midterm? Yes, but that would be better than making too little of it.

The worst reaction would be to take for granted that “our voters” will automatically rescue the Democratic Party in 2016. Demography is not destiny. The party’s job right now is to find candidates and fresh ideas that Americans want to believe in.

Eugene Robinson’s email address is eugenerobinson@washpost.com.