We don’t have to wonder anymore what Barack Obama is going to do with all that cash he’s been raising.

SIDEBAR: Obama dropped in at the Nashville-area home of Al and Tipper Gore after Tuesday’s debate; he gave a four-minute speech and raised $900,000. But that is a paltry sum compared to the nearly $10 million Bloomberg reports he raised last month at “two celebrity-filled events in Beverly Hills, Calif.“ He also set a one-month fundraising record of $66 million in August. END SIDEBAR

Obama has bought time on CBS and NBC for what amounts to a 30-minute commercial in the waning days of the presidential campaign.

His campaign is also negotiating with ABC for the time.

Pundits say it’s a brilliant move. After spending months and millions on ads in battleground states, the spot will give Obama an opportunity to make his case directly to the voters. The move is meant to help ensure a win in the popular vote, regardless of what happens in the Electoral College: While the latter will win him the presidency, it’s the former that will enable him to govern.

It’s unclear how much this will cost the Obama campaign. Media outlets simply estimate that the buy “likely will amount to millions of dollars” or that it “is a multimillion-dollar expense.“

Bloomberg quotes a Democratic media professional in the Atlanta area as saying of the buy, “It’s got to be in the millions.“

We might not know how much the spot will ultimately cost Obama. But we do know that whatever it is, the cash-strapped McCain campaign, which remains within the public financing system and is limited to $84 million for the general election cycle, can’t afford it.

Consider this, from the Associated Press:

That Obama has the ability to buy such a huge block of prime time is a testament to his prodigious fundraising. He has not been shy about spending it.

On Monday, for instance, he spent $3.3 million in a single day of TV advertising. At that rate he will spend more than $90 million on ads through Election Day — more than all the money Republican rival John McCain has to spend on his entire fall campaign.

The Republican National Committee is raising record amounts of money and pitching in to help McCain. But, the AP story says, even with their combined resources, McCain and the RNC trailed Obama in ad spending last week by more than $6 million.

... Just last week.

Obama brushed off a reporter’s question yesterday about what he would discuss in the superad, set to air Oct. 29 at 8 ET. “We’re going to talking about it tomorrow,“ he said.

Given Obama’s insurmountable fundraising advantage, McCain had better start hoping that the World Series stretches to Game 6—which would be played on ... Oct. 29.