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For Democrats, the miserable 2014 election resembled one of those horror-movie sequels where the plucky survivor inexplicably finds herself back in the haunted house with Jason or Freddy.

Tuesday's resounding Republican sweep closely followed the script of the GOP's landslide in 2010, and it exposed perhaps even more deeply the limits of the modern Democratic coalition—while underscoring the party's persistent inability to convince enough whites that they will benefit from activist government.

But just as President Obama recovered from his party's 2010 rout to comfortably win reelection two years later, some cautionary 2016 signs for Republicans are buried within the rubble of this week's Democratic disaster.

From many angles, Tuesday's results tracked the 2010 outcome. Starting with a much higher number, Republicans didn't gain as many House seats this time, but they added more Senate seats (likely nine, awaiting final outcomes in Alaska, Louisiana, and Virginia). As in 2010, when Republicans won governorships in Michigan, Pennsylvania, and Wisconsin—states in the "blue wall" that have voted Democratic in at least the past six presidential elections—the GOP on Tuesday seized chief-executive positions in even deeper-blue Illinois, Maryland, and Massachusetts.

Voter preferences recorded in the Edison Research exit poll posted by CNN virtually reproduced the 2010 outcome. Pending possible small final adjustments, the national exit poll found that Republican House candidates captured 60 percent of whites, 10 percent of African-Americans, and 35 percent of Hispanics; the comparable 2010 numbers were 60 percent, 9 percent, and 38 percent. This year, Republicans won 43 percent of voters under 30, and 57 percent of voters over 65; the 2010 numbers were 42 percent and 59 percent. On Tuesday, 44 percent of voters approved of Obama's job performance and 55 percent disapproved—exactly replicating 2010.

This duplicate debacle offers Democrats pointed lessons. Perhaps the largest is that it was folly for so many Democratic candidates to try to ignore President Obama. The familiar adage that all politics is local is simply obsolete. Our political system is growing steadily more nationalized and parliamentary—which means that the name on the back of the jersey now often matters less than whether that jersey is red or blue.

Whether Democratic candidates campaigned with Obama or shunned him, they found him unavoidably on the ballot with them. In the national exit poll, 87 percent of voters who approved of Obama supported Democratic House candidates, while 83 percent who disapproved backed Republicans. In five Senate-race states with exit polls, Obama's approval rating exceeded his national average of 44 percent; Democrats won four of them. His approval rating was 44 percent or less in states where 17 other Senate races were run (South Carolina held two). If current results hold, Republicans will win all of those races except the ones in New Hampshire and Virginia. That pattern signals that if Democrats can't make a stronger case for Obama's record in 2016, disenchantment with him could sink the party again.

Another powerful lesson is that even with the best technology, Democrats remain dangerously dependent on a boom-and-bust coalition of young people and minorities, whose turnout is much lower in midterms than in presidential elections. Despite overheated predictions, Democrats performed almost exactly as well with millennial voters (including whites) and most minorities as they did in 2010 (although their performance did decline among Asians). But the share of the vote cast by those under 30 was 6 percentage points less in 2014 than in 2012; the minority share dropped 3 points. On both fronts, the pattern exactly followed the sharp falloff from 2008 to 2010, despite this year's huge Democratic investment in turnout.

That suggests Democrats cannot compete for Congress without more support from middle-class and older whites. In the national House exit poll, Republicans carried exactly three-fifths of whites, virtually unchanged from 2012 and 2010. That advantage was remarkably consistent. The only Democrat in a top-tier Senate race who carried a majority of whites was New Hampshire's Jeanne Shaheen, who won. Continuing their contemporary pattern, whites over 45 and those without college degrees broke especially hard against Democrats.

With their Senate victories in Colorado and Iowa, their strong showing in Virginia, their blue-state gubernatorial breakthroughs, and their competitive performances in several previously Democratic-trending suburbs, Republicans powerfully reasserted their ability to compete nationally. But winning governorships doesn't consistently predict presidential success in a state. And unlike in 2010, the GOP did not capture any new Senate seats from the 18 "blue wall" states underpinning the Democrats' Electoral College advantage. Even if Republicans in 2016 match Tuesday's dominant three-fifths showing among whites, they will almost certainly lose the White House if they can't also narrow the Democrats' traditional presidential-year edge with minorities—who could make up 30 percent of the electorate by then.

This week's results left Democrats facing tougher immediate questions. But each party's core dilemma remains unresolved: Democrats again have shown they cannot win enough whites to consistently hold Congress, while Republicans still have to prove they can attract enough minorities to win the White House.

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