Barack Obama and John McCain are pulling out all the stops as their long battle for the White House comes to a close.

Analysts have noted that Obama is on track to set a record in presidential advertisement spending. With just weeks to go until election day, he has about US$100 million in the bank and more donations are coming in by the second. In some states, the Democrat is spending several times more on TV, radio and newspaper ads than McCain, his Republican rival.

Obama has so much money in his coffers that he's even branching out from traditional media into online ads and video games. He has bought billboards that appear in the virtual environments of least 18 video games -- mostly sports titles like Madden NFL 09 and NBA 08.

"I think it's clear evidence that the Obama campaign has more money than they know what to do with," says Evan Tracey, a campaign media analyst.

Obama has even spent a reported US$1 million to buy a spot before the opening of the World Series.

With a clear cash advantage, Obama is also venturing into traditional red states and those carried by Bush four years ago. Media experts say people may believe they're not influenced by advertising, but the reality is more money for ads can make a difference in the outcome of an election.

"I don't think an ad in a video game is going to get a couch potato off their sofas, but people are influenced by ads even if they claim they're not," says Darrell West, a media analyst with the Brooking Institute.

Facing what appears to be a tough uphill battle to win the presidency, the McCain campaign has gone on the offensive in key battleground areas. Pollsters say he's facing tough odds, which aren't made any better by a smaller ad budget than his opponent.

The Republican Party has tried to pick up the slack, spending their resources on so-called "robo-calls" -- automated telephone calls. The pre-recorded messages link Obama with former radical William Ayers, someone Obama has said he has never known well.

But a backlash appears to be forming, even among conservatives who think the robo-calls and some of the attack ads go too far and aren't necessarily helping.

Republican Sen. Susan Collins, a Republican, has called on McCain to put an end to the negative ads, fearing she'll face a backlash from voters in her re-election bid.

"These kinds of tactics have no place in Maine politics," Collins' spokesperson Kevin Kelley said.

With a report by CTV's Joy Malbon and files from The Canadian Press