Republican White House hopeful Mitt Romney is losing favour among U.S. voters just three months ahead of his tough election battle with President Barack Obama, a new poll showed Wednesday.

The Washington Post-ABC News poll showed that 49 per cent of voters have a negative view of the former Massachusetts governor, up from 45 per cent in May.

Forty per cent of voters, meanwhile, see him in a positive light, practically the same proportion from the spring.

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In contrast, 53 per cent of voters said they had a favourable opinion of challenger Mr. Obama, while 43 per cent said they felt negatively about him.

By a margin of 53 per cent to 40 per cent, more key independent voters see Mr. Obama favourably rather than unfavourably. Fifty per cent of this group view Mr. Romney unfavorably, compared to 37 per cent who consider him favorably.

Mr. Romney has has a rough summer marred in part by a series of slip-ups during a trip abroad to Britain, Israel and Poland. He has also come under fire over his unwillingness to release his tax returns from before 2010.

Among supporters of his own Republican Party, 83 per cent have a good feeling about Mr. Romney but just 41 per cent feel "strongly favourable." Sixty-one per cent of Democrats meanwhile feel this way about their candidate.

The poll, carried out between Aug. 1 and Aug. 5 surveyed 1,026 adults. The margin of sampling error was plus or minus four percentage points.

A separate Quinnipiac University/New York Times/CBS News poll shows a tight race shaping up in the swing states of Wisconsin, Virginia and Colorado.

While Mr. Romney leads Mr. Obama 50 per cent to 45 per cent in Colorado, the president holds a lead over his rival in Virginia and Wisconsin.

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In Virginia, Mr. Obama is ahead with 49 per cent compared to Mr. Romney's 45 per cent. In Wisconsin, he dominates with 51 per cent over 45 per cent.

The new figures come as Mr. Obama heads to Colorado on the campaign trail Wednesday.

U.S. citizens cast their ballots on November 6.