WASHINGTON (AP) — A breeze of momentum on his side, President Barack Obama is moving to shore up support in a key state while he and rival Mitt Romney spar over how to transform a bitterly divided political culture and how to best ensure the financial and health security of older Americans.

With their first debate in less than two weeks, the two men and their campaigns have begun to engage at an accelerated pace, giving any rival's phrase outsize importance and freshly dissecting old policy fights.

Obama was traveling Saturday to Wisconsin, a state that his campaign had considered safely in his column but which Obama aides seem eager to fortify in case Romney's running mate, Wisconsin native and congressman Paul Ryan, can erode the president's support. The trip is Obama's first to the state since February.

Romney, faced with second-guessing within his own party over his strategy, was staying away from swing states Saturday and raising money in California instead, eager to recover his fundraising advantage. Last month, for the first time, Obama and the Democratic Party out-raised Romney and the Republican Party $114 million to $111.6 million.

Romney opened a new line against Obama, casting the president as a failed agent of change. Obama was countering by portraying Romney as an insider beholden to partisan and corporate interests. At the same time, Romney tried to put an end to an old controversy by releasing his 2011 tax returns and his past tax rates, reinforcing his place as one of the wealthiest candidates ever to seek the presidency. Obama sought to gain an edge with older voters and near-retirement baby boomers by renewing his criticism of Romney's Medicare proposals.

Obama enters the weekend with polls showing him in a near tie with Romney nationally. But a new Wall Street Journal/NBC News/Marist Poll shows the president with leads among likely voters of 8 percentage points in Iowa and 5 points each in Colorado and Wisconsin, all battleground states. Polls published earlier this week pointed to leads for Obama in Virginia and Ohio.

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In a potential opening for Romney, new state-by-state unemployment numbers show upticks in August unemployment in five swing states.

Romney seized on Obama's claim Thursday that he has learned that he cannot change Washington from the inside and instead must mobilize the public to pressure Congress from the outside.

"Over history there have been people that have changed Washington from the inside," Romney said at a rally Friday in Las Vegas. "And they've done it effectively by showing leadership from the top."

Obama countered with a new line of his own: "What kind of inside job is he talking about?" He suggested that Romney would rubber-stamp the agenda of congressional Republicans or let oil companies run the country's energy policy.

"We don't want an inside job in Washington," Obama said. "We want change in Washington."

Obama confronted the Romney camp from afar on Medicare, addressing an AARP conference in New Orleans by video conference from Virginia moments before Ryan appeared to accuse the Obama administration of weakening Medicare and failing to take tough measures to stabilize Social Security. Ryan was greeted with boos when he called for the repeal of Obama's health care law, which is closing a gap on prescription drug coverage for older Americans.

Obama delivered a detailed argument against Romney's Medicare plan, which would offer seniors a choice between traditional Medicare and a voucher-like system to obtain private insurance. Obama argued that seniors would still suffer because only the healthiest would benefit from purchasing private insurance, while older Americans with greater health care needs would face rising premiums under traditional Medicare.

"The entire infrastructure of traditional Medicare ends up collapsing, which means that all seniors at some point end up being at the mercy of insurance companies through a voucher program," Obama said.

As some Republicans urged Romney to re-energize his campaign, the candidate was headed to San Diego and Los Angeles on Saturday to raise money. On Sunday, he was campaigning in Colorado, a state where polls show Obama holds a narrow lead. Starting Monday, Romney and Ryan will spend three days altogether in all-important Ohio.

In choosing to campaign in Wisconsin Saturday, Obama was bracing his lead in a state that he won easily in 2008 but where Ryan has proven popular as a congressman. Some Republican pollsters detected an uptick for Romney in the state shortly after Ryan was named his running mate. Wisconsin's 7.5 percent unemployment rate is below the national average, but the state's manufacturing industry has been hit hard in recent years.

But public polls still show Obama with leads in Wisconsin. Obama recently has begun airing ads in the state and has sent Vice President Joe Biden there twice this month. Ryan has held events in the state three times since joining ticket, once with Romney along.

Obama's campaign is focused on running up big margins in Milwaukee and Madison, both Democratic strongholds. Obama and Romney will be closely watching the Green Bay region, a swing area that could tip the balance in a close contest.

On Friday, Wisconsin's Republican governor, Scott Walker, said that immediately after Romney chose Ryan as his running mate, the campaign displayed a new sense of enthusiasm, excitement and adrenalin.

"I haven't seen that as much lately," he said, "and I think they need to get back to that if they're going to win this election."

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Associated Press writers Julie Pace in Washington and Steve Peoples in Las Vegas contributed to this report.