NEW YORK — If television ad spending is any guide, the White House race will come down to nine states that have absorbed an eye-popping $350 million in commercials so far.

Colorado, Iowa, Nevada, New Hampshire, North Carolina, Ohio, Pennsylvania, Virginia and Florida, the largest and most diverse of these highly contested states, are where the ad dollars have been concentrated, and that’s been consistent this election season.

They account for 120 of the 270 electoral votes a presidential candidate needs to win. Barack Obama carried all nine states in 2008 when he beat Republican John McCain, but polling and the ad crush indicate all are highly competitive this time.

While the rest of the country is virtually ad-free, the Obama and Mitt Romney campaigns, along with a host of mostly Republican-leaning independent groups, are going at it in those really competitive states. Voters in just 67 of the country’s 210 media markets are confronted by campaign ads on local stations, according to the Kantar/Campaign Media Analysis Group, which tracks campaign advertising.

“People are seeing more spots in fewer states than they were four or eight years ago — more advertisers, and a lot more money is being squeezed into a smaller number of markets,” Kantar/CMAG’s Elizabeth Wilner said. “It’s been quite static all these months,’ adding that it’s “hard to imagine we’re going to look at a vastly different picture than we’re seeing right now.”

Polls have shown that Romney and Obama are running almost dead even for months in a race shaping up as vastly different from 2008, when Obama outspent McCain on the air by more than 4-to-1.

Obama opted out of the public funding system that year, and that allowed him to raise and spend freely on ads wherever he chose. McCain accepted public money and the spending restrictions that came with it. Determined to avoid such an imbalance this time, Romney has decided against public financing. Republican donors are pouring money into independent groups that can run ads as long as they don’t coordinate directly with Romney’s campaign.

No state has been flooded with more campaign advertising than Ohio, where an average viewer in the Cleveland television market is seeing about 87 presidential campaign spots a week. Florida is the second most heavily saturated, with viewers in the Orlando media market seeing about 70 campaign ads a week. Iowa is third.

New York-based political ad buyer Joseph Mercurio called the figures “unprecedented and astonishing.” He noted that a heavy advertising presence in a competitive statewide race normally would mean about 20 spots a week for an average viewer.

Mercurio said such heavy advertising in a state typically would cause polling numbers to shift. That hasn’t happened this time, suggesting voters have tuned them out or only a few remain undecided.

“The fact that people are being bombarded with ads in these states and the numbers aren’t moving means the voters are very set,” Mercurio said. “Some sort of massive event would have to happen to shake this up.”

The Obama campaign has laid out nearly $125 million on broadcast and cable TV spots so far and has reserved millions more for August and the fall. Other than $7.5 million spent on national ads, almost all the money has gone into the nine critical states.

The Romney campaign has spent just $45 million on television ads, but several conservative-leaning independent groups helped the candidate to match and at times exceed the Obama team’s advertising efforts.

Leading the way are American Crossroads and Crossroads GPS, both linked to Karl Rove, President George W. Bush’s longtime political adviser. American Crossroads has spent about $50 million on ads in the swing states, while Crossroads GPS, which does not have to disclose its donors, has spent more than $55 million.

A third group, Restore Our Future, has spent about $20 million in the key general election battlegrounds after helping bury Romney’s primary Republican rivals with negative ads during the nomination fight. This group was formed by several former top Romney advisers.

Americans for Prosperity, formed by the conservative billionaire brothers Charles and David Koch, has spent over $15 million in swing states and purchased $25 million more to run from the coming week into early September. It’s spent a more broadly than the others, buying advertising time in Minnesota, New Mexico and Wisconsin in addition to the nine major swing states.

The group’s upcoming buy includes New Mexico and Wisconsin but not Minnesota, which most strategists believe remains securely in Obama’s camp. With so much money to spend, Romney and his allies can afford to run ads in those states simply to bait the president’s team into spending money to defend itself.

The Obama campaign has not bought ads in New Mexico and has spent just about $600,000 in Wisconsin, suggesting his strategists don’t believe those states are in play. Obama won both in 2008 and they’re expected to stay Democratic this time.

The Republican National Committee has spent nearly $16 million in swing states on Romney’s behalf. The Democratic National Committee is raising money in conjunction with the Obama campaign but has not run a separate ad campaign.

A few independent organizations have advertised in swing states for Obama but none with the heft and firepower of the Republican-leaning groups. The biggest pro-Obama super PAC, Priorities USA Action, has spent about $20 million on ads and has reserved $30 million more to run ads in six states in the fall.

Wilner of Kantar/CMAG said the advertising patterns both camps follow after their conventions will signal which states they believe are truly in play.

“If Romney begins to gain momentum, Michigan and Wisconsin may become competitive and North Carolina might be less of a draw for the president,” Wilner said. “If the momentum is with Obama, we might see him advertise in Arizona. Both sides will stay off the air in Michigan, remain on the air in North Carolina, and do only low level advertising in Pennsylvania.”