What is this, Stockholm Syndrome?

The latest polling data from Harvard’s Institute of Politics should be discouraging to Democrats, who have traditionally been able to depend on young bleeding-hearts for electoral support: A majority of 18- to 29-year-old likely voters now say they would prefer a Republican-controlled Congress to a Democratic one, by a margin of 4 percentage points. That’s true even though those very same voters say Democrats in Congress are doing a better job than their Republican counterparts.

To be fair, both parties get pretty lousy marks from young likely voters: Democrats received a 35 percent approval rating, while Republicans got 24 percent.

But even so, my generation’s stated preferences are perplexing: We millennials apparently want to be ruled by the party we think is the greater of two evils.

This makes even less sense when you consider how the GOP has treated politically engaged millennials.

For years, in states such as North Carolina, Maine, Ohio and Texas, Republican politicians have tried to make it systematically harder for young adults to cast ballots or even register to vote. Sometimes these suppression efforts blanket broad swaths of voters likely to vote Democratic (by curtailing early voting, for example). But some efforts specifically target young people (ending pre-registration for 17-year-olds who will be 18 by Election Day, threatening to cut funding for universities that help out-of-state students register to vote, etc.).

History suggests this is a good strategy for Republicans. The young are not universally Democrats — about half now call themselves independents — but in recent decades they have reliably awarded a majority of their votes to Democrats. In 16 of the last 19 federal elections, 18- to 29-year-olds favored the Democratic House candidate, according to exit polls. And the margin they’ve given to Democrats has been especially large in the past decade: In 2012, Democratic congressional candidates beat Republicans by a 22-point margin among the under-30 crowd. Strong turnout among the young has swung major elections away from Republicans, too; without their vote, Ohio, Florida, Pennsylvania and Virginia would have all flipped from Obama to Romney in 2012.

Given young people’s voting records, and Republicans’ efforts to suppress the youth vote altogether, why are millennials suddenly turning into Republicans en masse?

The answer is they aren’t. If you look at the entire universe of young people in Harvard’s poll — not just respondents who say they’ll “definitely” vote but also those who say they’re less likely to vote — they say they would prefer a ­Democratic-led Congress to a Republican-led one.

That is, the young overall still skew Democratic, just as history would predict. Many are just not motivated enough to act on their stated political beliefs by actually casting a ballot.

Voter turnout rates among the young almost always disappoint, especially in midterm years. In federal elections over the past five decades, turnout rates for 18- to 24-year-olds during midterms have averaged about half their rates during presidential elections (22 percent vs. 42 percent). The drop-off in other age groups isn’t nearly as big (among people over 65, it falls from 67 percent to 59 percent).

It just so happens that this time around, the youth turnout drop-off will be especially strong among Democrats. Exactly why is unclear. Maybe Republican efforts to suppress the youth vote have been more successful and targeted than anyone anticipated, with young Democrats across the country deciding that it’s just too much trouble to find the necessary paperwork and time required to vote. I’m not terribly convinced by this explanation, given everything else we know about attitudes of the young toward forbidden fruit. Young liberals who are aware of scheming to suppress their votes might be all the more motivated to cast a ballot.

I think young people just feel abandoned by Democrats. With youth joblessness rates still crazy high, recent college graduates groaning under the weight of student loans and millennials frequently blamed both for their own underemployment and the country’s overall economic woes, Democratic promises of hope and change have lost their shine. On lots of (mostly social) issues, millennial views comport more closely with the Democratic platform than the Republican one, but of all current generations, millennials are least likely to say they see much difference in the two parties.

Maybe the best form of youth voter suppression isn’t a voter ID law, long lines or closing the polls early. It’s convincing millennials that our presumed leaders don’t give a damn about us.