NEW YORK — Independent groups working to elect Republican Mitt Romney have helped him match or even exceed President Barack Obama’s TV ad spending in dozens of media markets in battleground states. But the spending disparity doesn’t tell the whole story, as Obama is still getting more value for his money with his ads.

An Associated Press analysis of presidential campaign advertising data from April through last week found that pro-Romney spending has exceeded pro-Obama ad spending by at least $65 million across the nine states expected to decide the election: Colorado, Florida, Nevada, New Hampshire, North Carolina, Ohio, Virginia, Iowa and Wisconsin.

Republican outside groups like American Crossroads and Americans for Prosperity have spent millions to complement Romney’s campaign advertising, helping the GOP hopeful break even with or surpass Obama in places the president once dominated.

Obama has gotten a boost from Democratic-leaning groups like Priorities USA Action, a “super” political action committee supporting his re-election, but not enough to tamp out the GOP-leaning advantage.

Romney’s allies have dropped millions of dollars in key swing state media markets. Without that assistance, pro-Obama spending would have outpaced pro-Romney spending in more than three dozen media markets.

Obama and groups supporting his re-election have spent more than $14.5 million on television ads in Las Vegas, about twice what Romney has spent. But GOP outside groups have dumped an extra $10 million into the market, allowing pro-Romney ads to outstrip pro-Obama TV spots there by $2.6 million.

In Washington, D.C., the main media market for voter-rich northern Virginia, Obama has had a $9 million advertising advantage over Romney. But an additional $13 million in outside ad spending, mainly from Crossroads GPS and Restore Our Future, put overall pro-Romney spending at a $29.6 million, besting the $25.9 million Obama has spent in that market.

Obama has more than doubled what Romney has spent on ads in Tampa, Fla. But $12 million in GOP outside money has poured into the market to help Romney, bringing pro-Romney spending to $19.7 million — about the same as what Obama has spent there.

Yet despite the onslaught, Obama has retained an overall advertising advantage over Romney and Republican groups. Under federal law, television stations must offer presidential campaigns a discounted price — it’s known as the lowest unit rate — to run their spots in the two months leading up to Election Day. Independent political groups aren’t eligible for the discount, so their ads cost as much to run as do commercials for products like Pepsi or Tide.

The Obama team has taken full advantage of the lower ad rates available to them, having booked their fall advertising last July and August to ensure placement on key shows in top markets. The leading Republican independent groups, American Crossroads and its affiliate Crossroads GPS, also placed their fall ad buys in the summer, but they are paying far higher rates for the same time slots as the president.

For example, American Crossroads had to pay nearly double what Obama’s campaign was charged — $1,400 compared with $765 — to run an ad during Tampa’s morning news program on Fox affiliate WTVT, a review of station records showed. Crossroads bought about four spots (compared with Obama’s three) during the 8 a.m. weekday slot.

The pro-Romney super PAC Restore Our Future did not make its bookings in the summer and is placing ad buys just days before the spots air, jacking up prices even more. In Norfolk, Va., last week, ROF paid $10,455 to air an ad on CBS station WTKR during the Tuesday prime-time, crime drama “NCIS” — more than double the $4,705 the Obama campaign was charged for the same show.

The Obama campaign also retains an advantage over the Romney campaign when it comes to ad placement, even though both campaigns are entitled to the discounted rate.

Romney’s campaign, like its independent ally Restore Our Future, places orders for its TV commercials just a few days before they are set to run. That means fewer ad slots are available to the campaign on a given day and in a given market, forcing the Romney team to pay more than the low rate it is eligible for if it wants to bounce another ad out of a time slot.

Romney’s ad-buying pattern was on display again this week. On Monday, the campaign still had not placed ad buys in three swing states — Nevada, New Hampshire and Ohio — for spots that were supposed to start running on Wednesday.

Romney campaign officials acknowledged the strategy has cost more money at times but said it allowed them greater flexibility to place ads where and when they need them, and to target the ads to demographic groups depending on what their polling shows.

Still, the strategy does have disadvantages. In Cincinnati this month, the Obama campaign paid about $175 to NBC station WLWT to air an ad on “Late Night with Jimmy Fallon.” Romney’s team spent nearly double that, $300, to run an ad on the show.

In Columbus, Ohio, this month, the Obama campaign paid WSYX, the local ABC affiliate station, $300 to run a 30-second ad during “Good Morning America.” The Romney campaign paid $550 for a similar ad that week, while American Crossroads paid $800.

“Just because the Republican side is stronger on dollar value, they’re not stronger on audience size,” said Joe Mercurio, a New York-based political media buyer. “Because of the way his campaign is buying, Romney has a smaller audience and his message to some degree is being polluted because the super PACs are muddying things up.”