This has to be the most racially polarised presidential election in decades

The 2012 election is shaping up to be more polarised along racial lines than any presidential contest since 1988, with President Barack Obama experiencing a steep drop in support among white voters from four years ago.

At this stage in 2008, Obama trailed John McCain by seven percentage points among white voters. Even in victory, Obama ended up losing white voters by 12 percentage points, according to that year's exit poll. But now, Obama has a deficit of 23 points, trailing Republican Mitt Romney 60 per cent to 37 per cent among whites, according to the latest Washington Post-ABC national tracking poll.

That presents a significant hurdle for the President – and suggests he will need to achieve even larger margins of victory among women and minorities, two important parts of the Democratic base, in order to win re-election.

Overall, Romney has edged ahead in the contest, winning 50 per cent of likely voters for the first time in the campaign. The President stands at 47 per cent, his lowest tally since before the party conventions. The three-point edge gives Romney his first apparent – but not statistically significant – advantage in the national popular vote. The challenger has a clear, nine-point lead when it comes to whom voters trust to handle the economy, which has long been the central issue of the contest. He has also effectively neutralised what has been a consistent fall-back for Obama: economic empathy.

Romney's momentum in these areas comes from improvements against the President among white voters. The slippage among whites is a setback for Obama, who campaigned on bridging the racial divide in his election and has sought to minimise rifts that have arisen in his presidency. Although Democrats typically win minorities and fare worse among white voters than Republicans, Obama outpaced previous losing Democratic candidates with both groups.

Just over a week before the election, the evidence suggests a more sharply divided country will head to the polls. As he did in 2008, Obama gets overwhelming support from non-whites, who made up a record high proportion of the electorate four years ago. In that contest, 80 per cent of all non-whites supported Obama, including 95 per cent of black voters, according to the exit poll. In the Post-ABC tracking poll, Obama again wins 80 per cent of non-whites, and support for his re-election is nearly universal among African Americans. In other words, Romney appears to have made no inroads into Obama's support among African Americans or Hispanics.

Dismal support for Republicans among minorities is a long-term problem for the GOP in a rapidly diversifying nation. Fully 91 per cent of Romney's support comes from white voters. The erosion of support Obama has experienced has been particularly acute among white men, whites without college degrees and white independents, the new tracking poll found.

In a rapidly diversifying country, the percentage of the nation's population that is white drops 2 per cent every four years, said David Bositis, a senior research associate at the Joint Center for Political and Economic Studies. And even among white voters, Republicans perform best among older people, who will, with time, drop off the rolls. Without improving minority votes, said Bositis, "this will be the peak for Republicans. The formula they have right now is a long-term loser."

In 1988, the last time there was such a prominent racial gap, white voters sided with George Bush Snr over Michael Dukakis 59 per cent to 40, with non-whites breaking 78 per cent to 20 for the Democrat. Were Obama to slip down into the 30s among white voters this year, it would be the first time for a Democrat in a two-way race since Walter Mondale did so in 1984, losing white votes to Ronald Reagan 64 per cent to 35.

The writer Polling Editor at The Washington Post