WASHINGTON - To become the nation's first black president, Barack Obama not only won heavy percentages of the black and Hispanic vote but also managed to trim the Democratic Party's traditional deficit among white voters.

Four years after Sen. John Kerry (D-Mass.) lost the white vote by 17 percentage points, Obama lost it by 12, according to exit polls.

While the 2008 gains were generally attributed to Obama's strength with young voters - he won by 10 points among whites aged 18 to 29 - he managed to improve on Kerry's showing with white voters across every age demographic.

Fast-forward to today. With the November midterm elections less than four months away, Obama's standing among white voters has sunk, leading some party strategists to fret that the president's erosion - and the party's - could adversely affect Democrats' chances of holding on to their House and Senate majorities.

"Since in the past House elections white voters tended to represent the independent vote, (the midterms) will surely be devastating for Democrats running in an election that will be a referendum on the Obama agenda," predicted one senior Democratic operative who closely tracks House races.

In Washington Post-ABC polling, Obama's approval rating among white voters has dropped from above 60 percent to just above 40 percent. In a June poll, 46 percent of white voters under 40 approved of how Obama was doing, compared with just 39 percent of whites 65 and older.

To avoid such losses, the Democratic National Committee has committed to spending tens of millions of dollars to re-create (or come somewhere near re-creating) the 2008 election model, in which Democrats relied heavily on higher-than-normal turnout from young people and strong support from African-American and Hispanic voters.

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