FILE - In this April 18, 2012 file photo, Republican presidential candidate, former Massachusetts Gov. Mitt Romney waves to supporters in Charlotte, N.C. The summer political lull will be a difficult one for the candidates _ not because it's crowded but because it's not. It could be a bigger problem for challenger Mitt Romney than for President Barack Obama, as it often is for those who must attract attention and stir up enthusiasm while voters are turned out before the fall election. (AP Photo/Chuck Burton, File)
WASHINGTON (AP) — The long, grueling GOP primary race is over. Now comes a summertime lull the candidates could find just as difficult — not because the schedule is crowded but because it isn't.
It is four months until the Republican National Convention in Tampa, Fla., in late August. Democrats hold their convention a week later in Charlotte, N.C.
That's a long time to fill, with no votes that matter, no debates to draw national attention. Voters tend to hibernate politically from the end of the primary season to the start of the conventions.
That lull should be a bigger problem for Republican challenger Mitt Romney than for Democratic President Barack Obama. A challenger must keep stirring up enthusiasm if he hopes to oust an incumbent president.
Romney has to figure out how to make news as he raises money and rallies supporters. He'll also be busy fleshing out a national organization and wooing disaffected conservatives — at the same time he's courting independents and other voting blocs where polls show he trails Obama, such as among women, Hispanics and young voters.
He'll pick a running mate at some point, and that's sure to ignite a burst of attention.
But it's not always entirely positive — as Republican John McCain found in 2008 with Alaska Gov. Sarah Palin or as George H.W. Bush learned in 1988 after he picked Indiana Sen. Dan Quayle. So Romney may tread carefully in making his choice.
Obama, meanwhile, gets a lot of free coverage just from being president and doing things presidents do both domestically and internationally.
"The challenge is a tough one, especially for the non-incumbent," says longtime Republican consultant Ed Rogers. "There's a news hole to fill every day that's bigger than ever. So you've got to feed that. And if you don't, then you're vulnerable to being picked apart with gaffes becoming stories, becoming metaphors that become the narrative of your campaign."
Furthermore, for Romney "this is a vulnerable period where he's coming out of the primaries kind of scuffed up and doesn't have a general-election infrastructure yet," Rogers said.
But some worries lurk for Obama, too. The economic recovery remains fragile. If it gets stronger, that would clearly help Obama. But the reverse is also true. If the economy worsens, it could hurt the president's chances.
And with the suspense gone from the GOP race, attention recently has shifted to scandals at the General Services Administration and the Secret Service, both more likely to hurt Obama than Romney.
The Obama campaign has shifted into overdrive to try to redefine Romney before he has a chance to better define himself.
The White House and Obama's Chicago-based re-election campaign have been moving away from echoing earlier GOP criticism that Romney lacked a core set of beliefs. Now, they're trying to make sure neither Romney nor the public forgets things he said to win over conservatives, including declaring in a speech that he was "severely conservative."
By all accounts, he governed Massachusetts as a political moderate. But that's not stopping Team Obama from painting him as a right-wing extremist.
"Romney and (his) party have gone way off to the right," says Obama campaign adviser David Axelrod. "A lot of Republicans in Congress want to cooperate and know better, but they're in the thralls of this reign of terror from the far right."
Romney is now the all-but-certain Republican nominee after his five-state sweep last Tuesday, and he has stepped up coordination with the Republican National Committee.
Newt Gingrich plans to suspend his campaign this week, leaving Texas Rep. Ron Paul the lone remaining Republican challenger to Romney. But Paul has few convention delegates.
Twenty-four more primaries and state conventions are scheduled through July 14, including delegate-rich contests in Texas on May 29, and in California and New Jersey on June 5. But they're basically cleanup exercises for Romney, who is now fewer than 300 delegates from the 1,144 needed to secure the nomination. He could get them by late May.
Romney will devote much time in coming weeks to raising money, aiming to pick up roughly $800 million by November. He and Obama are declining federal campaign financing for the general election — and avoiding its spending limits. It will be the first time both major-party candidates have done so since the program started in 1976. Obama raised a record $750 million for his 2008 presidential campaign. So far this year, he's running ahead of Romney, but the gap is closing.
It will be the most expensive election in U.S. history, even before considering the tens of millions to be spent on both sides by the new super PACs, which are able to take in limitless amounts of money and yet operate almost like an extension of a candidate's team.
For Obama, the coming months will mark his full-bore entry into the race for a second term. While he has been wooing donors at fundraisers for many months, he'll start doing official re-election campaign rallies on Saturday in Ohio and Virginia.
Obama's travel — both official and campaign — is also expected to pick up, with a West Coast swing already planned for May. Even events billed as "official" travel are likely to take on a campaign feel, as happened last week with Obama's two-day trip to college campuses in the battleground states of North Carolina, Colorado and Iowa.
The Obama campaign will also use the coming months to amplify its portrayal of Romney as an out-of-touch protector of the rich.
Romney will press his business credentials, claiming he knows how to create jobs while Obama doesn't.
While Romney advisers admit Obama's bully pulpit is larger, they've adopted a strategy of shadowing as many of his events as possible to stay in his face.
Steps Romney must take next "have to do with the basics of the ground operation. Get people registered to vote. Get offices going behind the scenes as well as have periodic speeches on major policy," said James Thurber, a political scientist at American University. "It's a very hard thing to do, to keep interest going and conserve money and not make mistakes."
The general election campaign shifts into high gear after the conventions. Obama and Romney will meet for three debates — on Oct. 3, Oct. 16 and Oct. 22. The vice presidential candidates will debate on Oct. 11.
Associated Press writers Steve Peoples and Julie Pace contributed to this report.
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