Washington (CNN) -- For both presidential campaigns, Republican Mitt Romney's choice of Wisconsin congressman and conservative star Paul Ryan as his running mate was like Christmas come early.
Conservatives wanted one of their own on Romney's ticket and they got that in Ryan, who has emerged as their ideological leader on the Hill on fiscal and budget matters. The choice also helps satisfy Republican strategists who felt Romney needed to not only stress how President Barack Obama has failed in that role, but also better articulate what the GOP candidate would do if elected.
"Ryan is a great choice. He energizes an already motivated party to a further degree and will help clarify the differing visions between the two campaigns for the country," said Phil Musser, a GOP strategist who in 2007 was a senior adviser to Romney's presidential campaign. "There are big choices, and in making the selection, Romney is showing that he believes America is ready for the choice."
But Romney's choice of Ryan also helps Obama better define what he's running against -- his campaign immediately made the Wisconsin congressman and his "extreme" budget a target and tied Romney's campaign to Ryan's House Republican colleagues, who he says wants to get rid of regulations on big corporations and give more tax breaks to the wealthy at the expense of the middle class.
Romney's introduction of Ryan dominated the news over the weekend with debates of the Wisconsin congressman's policy positions playing over the visuals of Baby Boomer Romney and Generation X'er Ryan appearing together in front of large crowds.
In many ways, Ryan is an "in-your-face" choice, said Ron Bonjean, a Wisconsin native, GOP strategist and partner at the political communications firm Singer Bonjean Strategies. Ryan's selection forces the Obama campaign to pivot from attacks on Romney's tenure at private equity firm Bain Capital and refusal to release more tax returns and focus instead on debating solutions to shore up the ailing economy.
Romney has campaigned largely on being critical of Obama's performance in office. However, this summer Romney has been hampered from expanding the conversation to the economy because he had to fend off the Obama campaign's questions about tax records and attacks on the former Massachusetts governor's private sector record.
The days leading up to the Ryan announcement had shown that the attacks were having an effect: Obama appeared to be opening up a lead in most head-to-head polls. But even more troubling, Romney's unfavorable numbers were creeping up after weeks of attacks by the Obama campaign and those supporting it.
"The choice of Ryan allows the campaign to better paint a picture of exactly what the campaign believes in terms of fiscal responsibility," said Bonjean, who first became familiar with Ryan while working in congressional leadership offices. "The Obama campaign started to define Romney and began to create a negative choice between the two campaigns. Picking Ryan hits the reset button for the campaign. It resets the campaign on policy terms. It takes away the politics of personal destruction that Obama was using and resets the campaign to talk about the two policy visions."
But there are pitfalls for the Republican ticket in picking Ryan.
Ryan's controversial entitlement reform plan, "Path to Prosperity"-- proposes a partially privatized Medicare program for future seniors. Instead of automatic enrollment in the government health care program for seniors, Ryan would give older Americans the option of buying into Medicare-approved plans with "premium support" payments or vouchers, as Democrats have described them.
It is a proposal that Romney has not fully embraced, telling surrogates in a talking points memo obtained by CNN on Saturday: "Gov. Romney applauds Paul Ryan for going in the right direction with his budget, and as president he will be putting together his own plan for cutting the deficit and putting the budget on a path to balance."
Obama was quick to pounce on Ryan as a veep choice. His selection makes the race a choice between two starkly different visions of the future in the country, the president said.
"My opponent and Congressman Ryan and their allies in Congress -- they all believe that if we just get rid of more regulations on big corporations and we give more tax breaks to the wealthiest Americans, it will lead to jobs and prosperity for everybody else. That is what they are proposing," Obama said at a fundraiser in his hometown of Chicago on Sunday.
"That is where they will take us if they win. This is not speculation. It's on their websites and embodied in the budget that the House Republicans voted for repeatedly."
Obama campaign senior adviser David Axelrod said on CNN's "State of the Union" on Sunday that Ryan is a "perfectly genial and bright guy," but at the same time a "right-wing ideologue, and that is reflected in the positions that he's taken."
On Monday, Axelrod compared Romney's and Ryan's budget plans.
"For the middle class it feels like a choice between a punch in the nose and a knee to the groin," he told CBS. "The fact is both plans call for trillions and trillions of dollars of new tax cuts skewed to the wealthy."
It's a refrain Democrats will try to hammer home in the weeks leading up to the Republican National Convention, said Christopher Arterton, a professor of political management at George Washington University's Graduate School of Political Management.
"The Democrats are trying to paint Ryan as an ardent conservative outside the mainstream of the U.S. in a way that they've not been able to make stick with Romney," Arterton said. "This allows them to say 'When you buy Romney, you buy a whole party with a whole philosophy that brings us back to the economic crisis of 2008.' "
Obama's campaign and its surrogates jumped on Ryan's controversial plans for entitlement programs as written in the GOP budget plan that he authored. Republicans say the cuts are necessary to bring down debt, but Democrats say the cuts shift the burden of safety-net programs to the middle-class and the elderly.
For all the energy and enthusiasm that Ryan brings to the ticket, those positions might make it harder for Romney because they could split the coalition that Republicans have made with blue-collar voters and the elderly, said Ron Brownstein, a CNN contributor and editorial director of National Journal.
"The modern GOP coalition is much more dependent than it used to be on both blue-collar and older voters," Brownstein said Monday on CNN's "Starting Point."
While they don't like welfare, food stamps and other "transfer programs," said Brownstein, "they are much more supportive of middle-class entitlements."
Indeed, Obama's campaign posted a Web ad in Florida ahead of Romney's bus tour through that state on Monday -- without Ryan, who was campaigning on his own in Iowa -- pointing out what it says would be the costs to seniors if Medicare became the voucher program that Ryan advocates in his budget plan.
For the next few weeks, both parties will battle over defining Ryan and what he stands for, Arterton said. A CNN/ORC International survey taken August 7-8, showed 54% of those polled saying they didn't know enough about Ryan to form an opinion
"He is kind of the proverbial blank slate on which both sides are trying to write their message as the public try to figure out who he is," Arterton said.
CNN's Jim Acosta, Peter Hamby, Athena Jones and Kevin Liptak contributed to this report