Barack Obama is overwhelming John McCain in the television advertising war, according to new figures released yesterday, swamping his opponent's efforts in many battleground states as their race enters its final stretch.

The rapid intensification of Mr Obama's advertising campaign comes as a series of new national polls showed him widening his lead over Mr McCain, amid signs that voters believe the Republican has spent too much time attacking his opponent and not enough explaining how he will tackle the economic crisis.

Accusations by Mr Obama that his rival has been erratic in how he has responded to the economic crisis also appear to have resonated with voters.

According to new figures, Mr Obama spent $42 million (£24 million) on television in 17 battleground states between October 7 and 13, compared with $10 million spent by Mr McCain in 14 states.

In the Washington DC area the Democrat ran 1,342 television commercials in the first three weeks of September - compared with just eight by his rival.

The strategy there is for the advertising blitz to spill over into northern Virginia, a state which has emerged as a critical battleground where Mr Obama leads in the polls.

Mr Obama has even paid for advertising to be embedded in 18 video games being sold in ten battleground states. The commercials, in games such as Guitar Hero, are aimed at men aged between 18 and 30. They remind them that early voting has begun and urge them to register and vote for Mr Obama.

The aggressive scope of Mr Obama's advertising is forcing Mr McCain to spend millions of dollars running commercials in states that Republicans won easily in recent presidential elections, including North Carolina, Indiana and Virginia, all now within Mr Obama's reach.

Last week Mr McCain spent $1.8 million in North Carolina, $800,000 in Indiana and $1.1 million in Virginia - states won twice by President Bush and where the Republican candidate is now being outspent significantly by his Democratic rival.

Three new national polls showed Mr Obama leading Mr McCain well outside the margin of error. A New York Times/CBS News survey put the Democrat ahead by 14 points, 53 to 39; a Pew Research poll gave him a ten-point advantage; a Los Angeles Times/Bloomberg survey had Mr Obama ahead 50 to 41.

The Pew survey showed that Americans are concerned about the economy to the exclusion of virtually every other issue, with 47 per cent saying Mr Obama could best address the current problems and only 33 per cent choosing Mr McCain.

Voters were especially critical of Mr McCain's performance in explaining how he would handle the economic crisis. Only 29 per cent say he has done an excellent or good job in explaining his approach to the crisis, while 67 per cent say he has done only a fair or poor job.

Andrew Kohut, president of the Pew Research Centre, described Mr Obama's lead as broad and consistent but said he believed the polls would tighten in the last 19 days of the race.

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