Democratic presidential hopeful Sen. Barack Obama is outspending his Republican opponent Sen. John McCain in fifteen critical states as Nov. 4’s election approaches, new figures show.

The Obama campaign spent over $17 million in TV ads from Sept. 28 through Oct. 4, while McCain spent just under $11 million, a new study by the University of Wisconsin-Madison Advertising Project reported Wednesday.

On Monday, Oct. 6, alone, the Illinois senator spent $3.3 million on television ads, while McCain’s ad spending totaled $900,000.

Both campaigns have been aiming at a series of battleground states, 10 of which were carried by President Bush in the 2004 election. The GOP nominee has been forced to defend himself in states such as Florida, North Carolina and Virginia, which have traditionally been strong Republican regions.

According to recent Real Clear Politics polling averages, Obama holds a 5-point lead in Virginia, a 3-point lead in Florida, and a 0.6-lead in North Carolina.

“The campaign is being played on the Republican side of the field this year,” ad project director Ken Goldstein said.

The McCain campaign has also been focusing heavily on Nevada, Colorado, Wisconsin and Pennsylvania, with the top two ad markets in the country being Las Vegas and Denver.

Obama’s decision to forgo public financing can partially account for this year’s increase in personal spending. Obama has spent more than $2 million each in Ohio, Pennsylvania, Florida and Virginia, while McCain has not spent more than $2 million in any state.

The ads the Arizona senator has been investing in appear to have a more negative tone than those paid for by his rival.

In the first week of October, 34 percent of Obama’s ads directly attacked McCain, according to the University of Wisconsin Ad Project. In contrast, “virtually all of McCain’s ads attacked Obama,” the Associated Press.

Obama’s 34 percent matches the percentage of negative campaigning that Kerry commissioned in 2004, but McCain’s 73 percent throughout his campaign is higher than President Bush’s 64 percent in the 2004 contest.

Despite the overall increase in negative ads by the campaigns this year, there has been a fall in the number of negative ads commissioned by outside organizations, TV Week reported.

“In 2004, a number of the negative attacks came from either independent groups or in some cases the political parties, while so far this year the candidates are doing far more of their own ads,” TV Week reported.