DES MOINES, Iowa (AP) — Newly tapped Republican vice presidential contender Paul Ryan is facing off against President Barack Obama as the front lines in the battle for the White House shift to Iowa.

While Mitt Romney continues a Florida bus tour, Ryan will meet voters at the Iowa State Fair, campaigning alone for the first time in the same state where Obama launches a bus tour of his own. Monday's events may help determine whether conservative excitement for the Wisconsin congressman — and his controversial budget plans — will overshadow Romney's own economic message.

Democrats are banking on it.

Since Romney formally named Ryan his running mate on Saturday, the Obama campaign has been attacking the Republican budget architect's plans to transform Medicare into a voucher system and re-shape the nation's tax system. That effort will continue as Obama kicks off a three-day bus tour across Iowa, making his longest visit to a single state yet as he seeks to fire up supporters who put him on the path to the presidency in 2008.

Ryan figures to play prominently in Obama's message.

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As Romney names running mate, voters wonder if VP pick matters; lessons from Palin in '08?

GILBERT, Ariz. (AP) — When a little-known Alaska governor stepped onto the American political stage as John McCain's running mate four years ago, the choice was intended to be a game-changer.

While Sarah Palin gave a boost to the Republican Arizona senator's presidential campaign initially, her campaign overall had mixed results.

Now voters and election watchers are trying to determine if Republican Mitt Romney's choice of Wisconsin Rep. Paul Ryan as his running mate will be a game-changer in this year's elections.

Those who have studied elections and vice presidential choices say the VP choice doesn't do much, if anything, to affect the outcome most years.

But they say it can make a difference in a very close race.

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GOP's Paul Ryan has bold plans for Medicare and Medicaid costs, but they've proved divisive

WASHINGTON (AP) — Republican Paul Ryan's blueprint for Medicare could prove as polarizing in the campaign as President Barack Obama's health care overhaul has been. Even Mitt Romney may not want to go there.

Romney's new running mate has built a strong reputation on Capitol Hill for bold ideas to restrain health care costs and federal spending overall. His centerpiece idea is to steer future retirees into private insurance plans, with a fixed payment from the government that may or may not cover as much of a retiree's costs as does the current program.

Ryan, a conservative Wisconsin congressman and chairman of the House Budget Committee, calls his idea "premium support." Democrats call it a voucher plan. In theory, Ryan's plan could work, economists say. But the devil's in the details. Lots of them, and yet to be ironed out.

Ryan would also turn Medicaid over to the states, and sharply limit the growth of future spending on that safety net program. Between them, Medicare and Medicaid cover about 100 million people, touching nearly every American family in some way.

While expressing support broadly, Romney has yet to spell out where he stands on specifics of his running mate's proposals. And that could get tricky.

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Strict school junk food laws may help curb kids' obesity, but study results aren't a slam-dunk

CHICAGO (AP) — Laws strictly curbing school sales of junk food and sweetened drinks may play a role in slowing childhood obesity, according to a study that seems to offer the first evidence such efforts could pay off.

The results come from the first large national look at the effectiveness of the state laws over time. They are not a slam-dunk, and even obesity experts who praised the study acknowledge the measures are a political hot potato, smacking of a "nanny state" and opposed by industry and cash-strapped schools relying on food processors' money.

But if the laws have even a tiny effect, "what are the downsides of improving the food environment for children today?" asked Dr. David Ludwig, an obesity specialist at Harvard Medical School and Boston Children's Hospital. "You can't get much worse than it already is."

Children in the study gained less weight from fifth through eighth grades if they lived in states with strong, consistent laws versus no laws governing snacks available in schools. For example, kids who were 5 feet tall and 100 pounds gained on average 2.2 fewer pounds if they lived in states with strong laws in the three years studied.

Also, children who were overweight or obese in fifth grade were more likely to reach a healthy weight by eighth grade if they lived in states with the strongest laws.

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EYES ON LONDON: London Olympics close with pomp and pop, eyes turn to Rio

LONDON (AP) — Around the 2012 Olympics and its host city with journalists from The Associated Press bringing the flavor and details of the games to you:

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RIO PREPARES

As the London Olympics closed, the next host, Rio de Janeiro, was set to kick off four years of preparations for games that some see as Brazil's entrance onto the world stage.

Many are bracing for a rocky ride as Rio — a laid-back beach city not known for its efficiency or punctuality — rushes to build four main Olympic sites and undertake a massive infrastructure overhaul.

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Golden Games: US wins the most medals, and the most gold, at London Olympics

LONDON (AP) — Red, white and blue was everywhere in London.

For the Americans — and for the British, too.

The most medals, and the most gold medals. That's what the U.S. Olympic Team wanted, and it's what they delivered. As for the home team? Riding the wave of home-field advantage, the British put together their best Olympic showing in over a century.

The competition is over. The U.S. was best, but the success stories from London truly spanned the globe.

"I think these games were absolutely fabulous," International Olympic Committee President Jacques Rogge said.

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With pop, performance and pride, London extinguishes Olympic flame and passes the torch to Rio

LONDON (AP) — And now, on to Rio!

London brought the curtain down on a hugely entertaining Olympics with a sensational rock 'n roll nostalgia tour of a closing ceremony that thrilled the London night with top-of-the-chart classics, supermodels and psychedelic mayhem.

After a glorious two weeks of never-to-be-forgotten moments that left Britain exhausted, exhilarated and deeply proud, organizers handed the baton to 2016 host Brazil, which must now take up the Herculean task of matching them.

Judging by the swaying samba of Marisa Monte and the sexy baritone of Seu Jorge in Brazil's eight-minute musical and visual postcard for the 2016 games, they look to be off to a foot-stomping start.

But Sunday was all about Britain.

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Mud, sweat and tears: Grueling obstacles courses draw millions, from chiseled to chubby

LONG POND, Pa. (AP) — More than 10,000 people trekked to northeastern Pennsylvania to scale walls, leap fire and crawl commando-style through a mud pit topped with barbed wire.

Willingly. For kicks. And they paid money to do it.

That's obstacle course racing for you: grueling, mud-spattered and, to its legions of fans, addictive fun.

In only a few years, obstacle courses have become a favorite diversion of thrill-seekers and weekend warriors, with hundreds of events around the country that require participants to go up, over, under and through to the finish line.

Three of the top series — Tough Mudder, Warrior Dash and Spartan Race — expect to host nearly 2 million runners in 2012, from fitness buffs bored with straight-line running to pasty 9-to-5ers blowing off steam with friends, from adrenaline junkies pushing the limits of their own physical and mental endurance to couch potatoes for whom working the remote more typically qualifies as exercise.

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Bo Xilai's case much more tricky for China's communist leaders than his wife's murder trial

BEIJING (AP) — Trying disgraced politician Bo Xilai's wife for murder was the easy part in cleaning up the political mess the couple has created for China's communist party leaders. Now comes the tough part: punishing Bo for abuse of power without further tarnishing the party's reputation.

Disciplining him quietly will save the party the embarrassment of washing its dirty linen in public but reinforce public perception that it goes soft on one of its own. Analysts say the leadership is therefore more likely to bite the bullet and try Bo in public in a nod to rule of law.

The first indication of this came when four Chongqing police officers were tried Friday for allegedly trying to help Bo's wife Gu Kailai cover up the murder of a British business associate, Neil Heywood, said Cheng Li, a China politics expert at the Brookings Institution in Washington D.C..

Chinese politics has a history of attacking subordinates to get at their superiors, and as part of the chain of command, the four can be directly linked to Bo, once the supreme communist party boss of Chongqing, a mega-city in China's east.

Li said the trial of the officers was a firm indication Bo would definitely face a judge, possibly in relation to the killing. "That's a statement that Bo Xilai will be charged," Li said.

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Rep: Jennifer Aniston is engaged to Justin Theroux

NEW YORK (AP) — After years of breathless anticipation — at least on the part of the tabloids — Jennifer Aniston is finally ready to wed again.

Her representative, Stephen Huvane, confirmed Sunday night that the actress is engaged to her boyfriend of more than a year, Justin Theroux.

"Justin Theroux had an amazing birthday on Friday, receiving an extraordinary gift when his girlfriend, Jennifer Aniston, accepted his proposal of marriage," said Theroux's rep in a statement to People, which first reported the engagement.

Theroux, 41, and Aniston, 43, have known each other for years, but started dating more than a year ago after working on the comedy "Wanderlust." Though that film disappeared quickly from movie theaters after its release earlier this year, the relationship clearly proved to have more staying power. The two moved in together and tabloids soon began predicting everything from marriage to babies for the new couple.

Aniston had been a part of such speculation for years, ever since the demise of her marriage to Brad Pitt after a five-year union in 2005. While Pitt moved on to a long-term relationship with Angelina Jolie, Aniston had high-profile relationships with the likes of John Mayer and Vince Vaughn that didn't last, leading to the common narrative: When will Jen find someone or have a child?