US election: Guide to the battle

Despite early talk of an expanded battleground map in the 2008 White House race, the McCain and Obama campaigns are now focusing their efforts on less than a dozen key states.

AD SPENDING IN KEY MARKETS John McCain: Philadelphia, $10.3m, Denver $6.3m, Washington, DC $4.4m, Cleveland $4.3m, Detroit $4.3m, Las Vegas $3.9m, Pittsburgh $3.6m Barack Obama: Washington, DC $12.9m, Philadelphia $11.9m, Denver $6.8m, Miami $6.2m, Detroit $5.4m, Cleveland $5.4m, Las Vegas $4.6m Source: Campaign Media Analysis Group up to 20 October US elections: Battleground map The shifting battleground

These include the traditional swing states of Ohio and Florida, which narrowly voted Republican in 2004.

But they now include a new group of southern states, such as Virginia and North Carolina, which were considered reliably Republican last time, and Western battlegrounds, such as Colorado, Nevada, and New Mexico, which had narrow Republican majorities.

The Obama campaign is also hoping to pick off Missouri, Indiana and West Virginia, previously considered solidly Republican.

The McCain campaign, which was hoping to make inroads in some Democratic states in the Mid-West, has been forced to pull out of Michigan and Wisconsin, but is still actively campaigning in Pennsylvania.

Spending on television advertisements indicates where the candidates are focusing their campaigns.

So far, Mr Obama has spent $182m on ads, compared to $118m for Mr McCain, according to the Campaign Media Analysis Group.

The top media markets for Obama campaign advertising were Philadelphia (Pennsylvania), Washington, DC (reaching Northern Virginia), Miami, Tampa and Orlando (Florida), Denver (Colorado), and Las Vegas (Nevada). There was also significant spending in the Mid West, including Detroit, Cleveland and Indianapolis.

The McCain campaign has nearly matched the Democratic spending in Denver and Las Vegas, and has also spent heavily in Pennsylvania, Ohio, Michigan and Minnesota. But it has been heavily outspent by the Democrats in Florida, Virginia and North Carolina.