The Economist’s Lexington columnist explains:

Working-class whites are angry with the Democrats for lots of reasons. Race is not one of them.

..the prospect of a Democratic rout prompts an inevitable question. Have such voters turned on the Democrats because Mr Obama is black? His election was hailed as proof that America had moved beyond race. And yet voting in the mid-terms will be polarised by race. Most whites will pull the Republican lever. Almost all blacks and most Hispanics will vote Democrat.

Race was a factor in 2008, and still is. Why else would blacks alone have stuck so staunchly by their man? As for working-class whites, they did not much care for Mr Obama even in 2008, preferring John McCain by a margin of 18%. But as Mr Obama campaigned, his colour seemed to count for less.

For 20 years Stan Greenberg, a Democratic pollster, studied the blue-collar white voters of Macomb County near Detroit. In 1984 they voted by two to one for Ronald Reagan because, Mr Greenberg found, when such voters heard Democrats talk about economic “fairness”, they saw this as code for transferring money to blacks. Nonetheless, in 2008 Mr Obama won Macomb County with a margin of eight points. Over the course of his campaign, the proportion of Macomb voters who said they were “comfortable” with the idea of Mr Obama as president rose from 40% to 60%. Having watched Mr Obama closely, Mr Greenberg concluded, they “became confident he would work for all Americans and be the steady leader the times required.”

If such voters have now changed their minds, the reason is not that Mr Obama is black—he was black in 2008. And for all its momentous symbolism, his election is not the most recent evidence that America has turned the page on race. In June, in South Carolina of all states, Tim Scott, a black Republican, defeated the son of the segregationist Strom Thurmond in a primary, and is on his way to a seat in the House. Compare that to 1983, when a disgraceful number of Democrats in Chicago voted for the Republican rather than send the black Harold Washington to city hall.

All of that has gone. The electorate may be divided by race, but no longer mainly because of race. Some of Mr Obama’s enemies have tried to harness pockets of bigotry by painting him in various ways as un-American. But outright racism in politics is now beyond the pale and will probably have little to do with the coming rejection of the Democrats by the white working class. A wrecked economy and the feeling that their president is out of touch are reason enough. It has, after all, happened before. In two short years from 1992 to 1994, when Bill Clinton was president, white working-class support for the Republicans soared like a rocket from 47% to 61%. Nobody blamed that on skin colour.

Years ago, in the middle of the Whitewater investigation, one heard the first murmurs: white skin notwithstanding, this is our first black President. Blacker than any actual black person who could ever be elected in our children’s lifetime. After all, Clinton displays almost every trope of blackness: single-parent household, born poor, working-class, saxophone-playing, McDonald’s-and-junk-food-loving boy from Arkansas.