The victory of Republican Karen Handel in the special election in Georgia’s 6th Congressional District on Tuesday has discouraged Democrats and encouraged Republicans. Democrat Jon Ossoff won 48.1 percent in the special election’s first round April 18, and Democrats had high hopes that they could take this House seat from the Republicans.

But even with $30 million spent — in what became the most expensive House race ever — and with a turnout of 260,000 (more than the 210,000 who voted in the 2014 midterm), Ossoff won exactly 48.1 percent again. Not quite enough.

Georgia’s 6th District was significant because it’s a traditionally Republican district whose college-educated voters (59 percent of adults, sixth-highest in the country) were repelled by Donald Trump. Mitt Romney carried it 61 to 37 percent in 2012; Trump won it by only a 48.3-46.8 percent margin last year. That’s a huge shift from the persistent partisan patterns that have mostly held for two decades.

The good news for Democrats is that they were able to hold Handel to a Trumpish rather than the traditionally expected margin in such a district. The bad news is that there aren’t that many other Republican-held districts with a lot of highly educated voters.

Republicans hold only six of the 23 districts with college graduate majorities. Most were won years ago by Democrats in elections in which the persistent partisan patterns held true. Of the Republican-held districts where 40 percent or more of the voters are college graduates, only 14 were carried by Hillary Clinton last year.

These 14 seats — plus the four more that Trump carried by less than 5 percent — are obvious Democratic targets, and the result in Georgia suggests that Democrats could be competitive in many of them. But Democrats need a net gain of 24 seats for a House majority, and in good years, parties usually gain only half the seats they seriously target.

Moreover, Republican incumbents won 15 of these 18 seats by double-digit margins in 2016 despite the local Trump undertow. Most or all are running again, and though Democrats may try to field stronger opponents against many, the Georgia result won’t help recruitment.

There’s a contrast between the special election in Georgia’s 6th District and the three other special elections in districts with far lower percentages of college graduates (23 to 31 percent) — Kansas’s 4th District, Montana’s at-large district and South Carolina’s 5th District. Trump carried all three by wider margins than Romney, but in each, Republicans failed to match his showing and won with results reverting toward or falling below the levels of the persistent partisan pattern.

This is often the pattern in special elections, wherein you can cast a protest vote without affecting the balance of partisan power much. And it’s especially true when, as in these examples, no one expects the incumbent party’s candidate to lose. That was the case Tuesday in South Carolina’s 5th District, where 87,000 voted — one-third the turnout in Georgia’s 6th District.

In off-year congressional elections, the dynamics are different. Incumbents enter with an edge and often without serious opposition. You can’t cast a protest vote without risking a change in party control, a risk that seems likely to be palpable in 2018.

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Michael Barone is a senior political analyst for the Washington Examiner, resident fellow at the American Enterprise Institute and longtime co-author of The Almanac of American Politics.