Democrats are riding high after apparently unseating GOP Gov. Matt Bevin in Kentucky and winning back majorities in both chambers of Virginia's General Assembly in Tuesday's elections. Just as in 2018, when Democrats took back the majority in the House, Democratic gains were concentrated in largely white, middle-to-upper income suburbs.

In Kentucky, Democrat Andy Beshear capitalized on Bevin's unpopularity to apparently win a state President Donald Trump had carried by 30 points, and the most dramatic erosion in Bevin's support occurred in the northern Kentucky suburbs. For example, in 2015, Bevin carried Kenton County, just outside Cincinnati, by 18 points. On Tuesday, he lost it by a point.

In Virginia, Democrats wrested control of the state Senate by flipping one seat each in the fast-changing, highly professional northern Virginia and Richmond suburbs. They also won control of the House of Delegates for the first time since 1997 by capturing two seats in northern Virginia — and at least three more seats in the Tidewater area that had been redrawn after courts ruled the previous GOP-drawn map was a racial gerrymander.

However, the results weren't as sparkling for Democrats in Mississippi, the least-white state at stake in Tuesday's major contests. Plain and simple, African American turnout there was weaker than expected — and that should serve as a warning to Democrats elsewhere.

It wasn't shocking that Republican Lt. Gov. Tate Reeves defeated Democratic Attorney General Jim Hood by 6 points for Mississippi's top job. But it was surprising that turnout in the Magnolia State's first competitive gubernatorial race since 2003 was so low. In Kentucky, turnout — as measured by total votes cast— surged a massive 51 percent over 2015's heated race, but in Mississippi it rose just 20 percent over 2015's uncompetitive contest.

In fact, turnout in Mississippi was down from last November's special Senate election, when GOP Sen. Cindy Hyde-Smith defeated Democrat Mike Espy 54 percent to 46 percent. The reason? Hood, a conservative white Democrat who had long served as the state's attorney general, failed to mobilize Mississippi's black voters to the same extent as Espy, who is African American and had represented the Mississippi Delta in Congress in the 1990s.

In Mississippi counties where white residents outnumber African Americans, 2019 turnout was down just 3 percent versus last fall and Hood took 39 percent, up from Espy's 37 percent. But in Mississippi counties where African American residents outnumber whites, 2019 turnout was down 8 percent and Hood took just 68 percent, down from Espy's 69 percent. In Jackson's Hinds County, the largest in the state, turnout was down 11 percent.

In the immediate future, this should be a major caution flag for Louisiana Gov. John Bel Edwards, another conservative white Democrat who faces a tight Nov. 16 runoff against Republican Eddie Rispone for a second term. One reason Edwards took just 47 percent of the vote in the initial voting round on Oct. 12 — shy of the majority required to avoid a runoff — was that the African American share of the electorate lagged behind 2015's share.

More broadly, driving up African American voting enthusiasm in the post-Obama era is also central to Democrats' chances of defeating Trump in 2020. After all, of the six states set to decide the 2020 election — Arizona, Florida, Michigan, North Carolina, Pennsylvania and Wisconsin — black voters are a robust share of the electorate in all but Arizona. Their engagement is critical to any Democratic path to victory in the Electoral College.