The McCain campaign has outspent the Obama camp by hundreds of thousands of dollars, and in some cases by as much as a million dollars or more, in virtually all of the dozen battleground states where both campaigns are up on the air, according to a firm that tracks national advertising.

Evan Tracey, the chief operating officer of TNS Media Intelligence/Campaign Media Analysis Group, confirmed to us in response to our questions that McCain's campaign has racked up a huge ad spending advantage in what he called "traditional battleground states," the states that both campaigns are sinking cash into.

McCain is advertising heavily in 12 traditional battlegrounds; Obama is advertising in those same 12 plus roughly seven more; and McCain holds a heavy advantage in virtually all the 12 shared states.

The comparison is significant, and in one sense it lends comfort to Obama, because McCain has not been able to pull ahead in those states despite vastly outspending him in them. But the flip-side of this is that Obama has not been able to make significant enough headway in many of the seven states where Obama has the airwaves to himself.

Here's the comparison of the two camps' spending on ads up to the present in the 12 states where both are up on the air, according to Tracey:

Iowa: McCain has spent roughly $700,000 more than Obama.

Missouri: McCain has spent roughly half a million more than Obama.

Ohio: McCain has spent approximately one million more than Obama.

Pennsylvania: McCain has spent roughly a million and a half more than Obama.

Michigan: McCain has outspent Obama by about a million dollars.

New Hampshire: Spending is about even.

New Mexico: McCain has spent approximately $300,000 more, and has outspent Obama by roughly two to one.

Nevada: McCain has outspent Obama by $800,000, also roughly two to one.

Missouri: McCain has spent $500,000 more than Obama.

Virginia: Obama has spent a million more than McCain, largely because Obama is advertising statewide while McCain is only up in a small part of the north.

Wisconsin: McCain has spent roughly a half million more than Obama.

North Dakota: Obama has outspent McCain by around $170,000.

The reason for this is partly that both campaigns are spending at roughly the same rate overall, but Obama is spread thinner and is spending in more states. Tracey says that the campaigns are both spending between $1 million and $1.6 million a day overall.

Meanwhile, Obama is up on the air in all of McCain's states, but also in Indiana, Alaska, Montana, North Carolina, Florida, Georgia, and southern Virginia.

"There are two ways to look at this," Tracey says. On the one hand, Obama is pouring significant resources into seven states where McCain is spending nothing at all, and hasn't necessarily gained enough in those states to show for it.

But Tracey adds that the spending disparity in the core battlegrounds also bodes well for Obama in some ways. "The concern for McCain is that he's outspending Obama" in the more traditional battlegrounds at a rate "that's not going to be sustainable," he says. "But he's not building any real leads in these states."

The Obama campaign may be banking on the fact that with enough spending in non-traditional states they can eventually force the McCain campaign to broaden the number of states they're spending in, making it tougher for the McCain team to keep pace with Obama's spending advantage this fall.

Late Update: Some of you rightly note that Colorado isn't on the list even though both campaigns are advertising there. We'll bring you word on Colorado's spending disparity as soon as we get it.

Separately, it's worth pointing out that the total list where both are up is still 12, even including Colorado. That's because Virginia shouldn't really be on the list, because McCain's advertising is very limited there regionally.

Late Update: We inadvertently left Colorado and Michigan off the list of states where both are advertising; they've now both been added, above. Also, North Dakota was accidentally described as a state where Obama is advertising solo; in fact, both campaigns are up on the air there.

Finally, we initially said that there are 11 states where both are up on the air; it's in fact 12 states, not counting Virginia, which is a special case because McCain is only up in a small northern corner of the state in order to access the D.C. market. Obama is up statewide there.