The reaction: In the region, both parties find reason to cheer.

Top Republicans and Democrats in the Philadelphia area saw reasons to cheer Paul Ryan's selection Saturday as Mitt Romney's running mate - but their reasons were markedly different.

GOP leaders said Ryan's sweeping proposals to cut taxes and spending offered voters intellectual heft on the fiscal issues at the center of the presidential campaign. Democrats proclaimed that they had been handed a ripe target and a chance to cast Ryan's support for Medicare cuts and upper-income tax breaks as the latest evidence that Romney is the candidate of the rich.

"Anyone who doesn't think this whole election is about the economy doesn't understand the election," said longtime GOP power broker Robert B. Asher, Romney's Pennsylvania campaign-finance chairman. "Ryan has proven that he has brilliant ideas in that area."

Added Sen. Pat Toomey (R., Pa.) in a news release: "Congressman Ryan is one of Congress' strongest voices advocating for economic growth through free enterprise and fiscal sense."

That the reaction split along party lines was no surprise. But some applied more verve.

Rep. Bob Brady, Philadelphia's Democratic Party chairman, said Ryan's selection showed Republicans were "serious about blowing up the middle class and the working class. It just locks them in their position to eliminate middle-class America."

"His ideas are all for the one-percenters," Brady told The Inquirer at Saturday's labor rally on the Parkway. "If we as Democrats don't wake up now, we will never wake up."

Rep. Frank LoBiondo (R., N.J.) said: "Let's face it. The Democrats would demonize Abraham Lincoln if he were the vice-presidential pick."

The back-and-forth in interviews and a flood of Saturday news releases foreshadowed arguments that are sure to be repeated between now and Nov. 6. Ryan, a Wisconsin representative and chairman of the House Budget Committee, has invigorated fiscal conservatives with bold ideas to slash spending.

Democrats see those ideas as a political paper trail they intend to set afire.

"He has put out a clear deficit-reduction plan. It's clearly wrong," said Rep. Robert Andrews (D., N.J.). "Gov. Romney has been ambiguous, it's not clear where he stands from day to day on a lot of things. Paul Ryan is very clear."

Rep. Allyson Schwartz (D., Pa.), one of the highest-ranking Democrats on the Budget Committee, said Ryan's plan drew "a clear distinction" with her party, which favors a mix of spending cuts and tax increases on the wealthy to bring the nation's budget into balance. Ryan's plan, she said, returns to failed Republican policies of the past.

"If they worked, we wouldn't be in this mess," Schwartz said.

LoBiondo, a longtime GOP representative, said Ryan "understands we're spending ourselves into oblivion," and aims to preserve Medicare by controlling its spiraling costs.

He said Ryan's plan, even with its inherent political risks, signaled seriousness about confronting entitlements. "President Obama has no plan. He has not talked about how he would keep Medicare solvent," LoBiondo said. "Paul Ryan has the ability to raise the caliber of the debate to being very substantive."

The same arguments are already trickling into local races. Democratic challengers in suburban swing districts quickly tried to tie incumbent GOP congressmen such as Patrick Meehan in Delaware County and Jon Runyan of Mount Laurel to their House votes in support of Ryan's plan.

"Today, middle-class families and seniors in the Third District will hear the warning alarms because the Ryan-Runyan budget received a national stage to follow through on their harmful agenda," said Shelley Adler, Runyan's Democratic challenger in South Jersey.

George Badey, the Democrat taking on Meehan in Philadelphia's western suburbs, said in a release that Romney's choice made Meehan's votes for Ryan's Medicaid plan "all the more real, serious, and dangerous."

Runyan and Meehan trumpeted Romney's decision. "Gov. Romney knows that we cannot continue down the irresponsible path of raising taxes on working families, small businesses, and seniors to pay for the runaway spending and borrowing of career politicians in Washington," Runyan said in a release.

Meehan predicted Ryan's selection meant "a campaign that focuses on the big issues about the direction of the country, how we create jobs and put our fiscal house in order."

The debate over whether Ryan would help solve those problems or exacerbate them began Saturday, with rhetoric across the region and the nation already at a boil.

at jtamari@phillynews.com or follow @JonathanTamari on Twitter.