Why is the Democratic Party losing white voters, which was quite evident in results of the 2014 mid-term election when Republican candidates made gains in both houses of Congress? White voters of all ages were less likely to back Democrats this year than in elections past, helping Republicans nationwide but most acutely in the South - and overpowering Democratic efforts to turn out their core supporters among blacks and Hispanics.
In a nation growing ever more diverse, political forecasters repeatedly warn Republicans they must improve their appeal among minorities in order to remain competitive in the long term.
But for the Democrats, dominating the vote among minorities isn't enough to win elections today - and it won't be in the future if the GOP is able to run up similar margins among whites, who still make up a majority of voters in every state.
"The rule of thumb was Democrats could win with 90 percent of the African-American vote and 40 percent of the white vote," said Merle Black, a political science professor at Emory University in Atlanta.
"But now very few Democrats could think about getting 40 percent of the white vote. They're trying to get 30 percent. In the Deep South states, from South Carolina to Louisiana, it's very hard for the Democratic candidate to get 25 percent of the white vote."
Republicans running for seats in the House won 60 percent of the white vote, while Democrats won the backing of 89 percent of African-Americans and 62 percent of Hispanics.
Those margins are nearly identical to the 2010 midterm elections. But Democrats won more of the white and Hispanic vote in 2006, the last midterm elections in which the party won control of the House. White voters last tilted in Democrats' favor in a midterm in 1990, and were a swing group in the 1980s.
The data on voters come from exit polls of voters nationally and in 27 states that were conducted for The Associated Press and the television networks by Edison Research. Most interviews were conducted among randomly selected voters at precincts nationwide and in each state.
Outside the South, whites broke for Republicans by an average of 8 percentage points on Tuesday. But in 10 Southern states with an election for Senate on the ballot, Republicans won the white vote by an average of 42 points. Democrats garnered so little support among whites in Georgia, Louisiana, Mississippi, South Carolina and Texas that a majority of those voting for the Democratic candidate were non-white.
In North Carolina, though incumbent Democratic Sen. Kay Hagan was widely credited with running a solid campaign, she carried just 33 percent of the white vote - down from 39 percent in 2008 - and lost. White voters under age 30 backed Hagan by close to a 2-1 margin six years ago as they helped sweep President Barack Obama into office.
This time, in a midterm election, the younger white voters who cast ballots in North Carolina broke just as decisively for Hagan's Republican opponent, state House Speaker Thom Tillis.
Steve Rosenthal, president of the Organizing Group, a Democratic-leaning consulting firm, said he's been jokingly calling this election the Seinfeld election for Democrats: They had no national message that resonated with their voters.
"It was an election about nothing. Republicans made it an election about President Obama. That was their goal," he said. "Their mission was to turn out people who were angry, people who were displeased with the job the president has done."
It was a mistake for Democrats to distance themselves from the president, said Erik Smith, a former Obama campaign adviser and Democratic strategist. Democratic voters are not motivated to help candidates who were happy to be with Obama two years ago, but tried to avoid his presence this year, he said.
"I'm sure (it) led a lot of these voters to say, 'How is this candidate going to treat me in two years?'" he said.
The only states in which Democratic Senate candidates improved their overall support among whites were Minnesota, Oregon and Mississippi, a Southern state where Travis Childers managed to grow the Democratic share of the white vote from 8 percent in 2008 to 16 percent.
Democratic voters were especially less engaged in states where there were not supposed to be competitive elections, said Michael McDonald, an associate professor of political science at the University of Florida who tracks voter turnout.
Democratic voters are traditionally more likely to stay home if the midterm races are uninspiring, while Republican voters - who tend to be older, wealthier and more educated and also are more likely to be white - generally come to the polls anyway, he said.
"The poster child for this would be Virginia. It's an uncompetitive race, according to all the polls. In that environment, who sits out the election? It's predominantly Democrats," McDonald said.
Two days after the election, while the heavily favored incumbent, Democratic Sen. Mark Warner, had a lead of a few thousand votes out of more than 2 million cast, the race remained too close to call.
Associated Press writers Connie Cass in Washington and Bill Barrow in Atlanta contributed to this report.
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Copyright 2014 The Associated Press.