WASHINGTON (AP) — Mitt Romney and his Republican Party raised $40 million in April, an unexpectedly strong haul in the first month of the general campaign that illustrates enthusiasm within the GOP and threatens President Barack Obama's overwhelming cash advantage.

Since becoming the presumptive Republican presidential nominee, Romney has devoted most of his time to privately courting donors so he can prepare for what may be the most expensive campaign in history. His focus appears to be paying off. In just one month, Obama's 10-to-1 cash advantage has shrunk to 2-to-1, partly because the Republican National Committee now is helping Romney. His fundraising numbers may offer the best evidence to date that weary Republican donors who spent months on the sidelines are finally opening their wallets for Romney after a long and bitter primary.

"Fundraising is going extremely well," said Woody Johnson, a Romney fundraiser and New York Jets owner. "This is a very motivated group of people who are giving to this campaign."

The former Massachusetts governor is putting that cash infusion to use quickly. He announced plans Thursday to go on the air soon with his first TV ads of the general campaign, a positive commercial intended to introduce him to voters. He was buying airtime in four of the most competitive battleground states: Iowa, North Carolina, Virginia and Ohio.

Romney's April fundraising figures — a sharp increase from March, when he pulled in just $12.5 million while fending off primary opponents — show that he and the Republican National Committee together raised nearly as much money as the president and the Democratic National Committee, which together brought in $43.6 million last month.

Perhaps more important, Romney's side reported $61.4 million in the bank. The most recent figure available for Obama and the Democratic National Committee showed $124 million on hand at the end of March.

Still, Romney's new numbers don't reflect millions of dollars more raised and spent by pro-Romney super political action committees to help the former Massachusetts governor.

Both Romney and Obama are busy stockpiling cash to make sure they have enough money to reach voters on television, the Internet, by mail and over the phone, and to support a network of staffers across the country.

Obama's team, which already boasts more than 600 paid staffers, has been working to strengthen its network on the ground for months. Romney is in the process of expanding his team.

"We're pleased with where we are. We've been able to build a great ground operation in states across the country, which ultimately is what we believe will decide the election," Obama's deputy campaign manager Stephanie Cutter said when asked about fundraising. She noted that the campaign so far has accepted donations from almost 2 million individuals who gave on average $50.

Romney's campaign, by contrast, says it has received donations from all 50 states and that 95 percent of individual donors last month gave $250 or less. The vast majority of the April haul, however, $30 million, came from donors giving more than $250.

The campaigns have released only partial fundraising details. Full financial reports aren't due to the Federal Election Commission until midnight Sunday. The filings will detail the names and personal information for all donors, providing new insight on the sources of each campaign's cash.

The reports will do little to shed light on spending by outside groups.

Earlier this week, the independent group Crossroads GPS announced a $25 million, monthlong advertising blitz against Obama in 10 states. The ad push is the latest to illustrate the degree to which the campaign is playing out under dramatically looser campaign finance laws after a series of Supreme Court decisions allowed independent groups to raise and spend unlimited sums as long as they don't coordinate directly with the campaigns they support.

The super PAC Restore Our Future, staffed with former Romney aides, has spent at least $4.3 million so far, while Americans for Prosperity, the group founded by brothers Charles and David Koch, has spent $5 million. The American Future Fund, whose goal is to promote conservative and free-market ideas, is spending an additional $4.7 million to run a one-minute ad suggesting Obama hasn't cracked down on Wall Street because of his campaign's fundraising.

All that help means Romney doesn't have to spend much of his own money to stay competitive on the air with Obama. He can spend time fattening his campaign account. To that end, he planned to join Johnson in the New York area this weekend for nearly three full days of fundraising.

Obama's campaign, meanwhile, can't count on much outside help, so he is spending $25 million of his campaign funds on a monthlong television ad push in the most competitive states.

Pro-Obama super PACs haven't brought in nearly what their counterparts on the right have, though one — Priorities USA Action — is spending $4 million to air ads intended to help Obama by attacking Romney.

Democrats downplayed Romney's strong fundraising month.

"We all see Romney as a formidable opponent. He's going to raise a lot of money," said Don Peebles, a member of Obama's national finance team. "I don't think the president needs a dramatic financial advantage. I believe the president will ultimately have one. And I don't believe one month will be reflective of the overall financial performance of Romney's campaign."