On Friday, President Obama was in Richmond hoping to show Americans that he has a plan to jump-start the economy. “Let’s just shake off all the naysaying and the anxiety and the hand-wringing,” he said. “Enough of that. Let’s get to work.” Tuesday, he’ll try in Columbus, Ohio, and on Wednesday, it’ll be in Raleigh-Durham, N.C.

But as he ventures outside the politically barbed confines of Washington, it is becoming increasingly clear that the monumental task of figuring out how to pay for his jobs plan will fall to the new special congressional committee already charged with the daunting task of reducing the deficit by $1.5 trillion.

Obama has asked the group, widely dubbed the “supercommittee,” to expand its mandate and come up with enough in savings to offset the costs of his nearly $450 billion jobs plan, as well.

The added burden has some members of Congress concerned that the group is now expected to be not just super but downright magical.

“It’s like they’re becoming the Twelve Apostles. They’re going to dictate the law,” said Rep. Raúl M. Grijalva of Arizona, a liberal Democrat who fears that the committee will recommend cuts he opposes. “It really worries many of us.”

Already, the bipartisan panel of six senators and six representatives has been trying to come to an agreement on a strategy to tackle the government’s debt by Nov. 23.

That meant the group was seeking a deal on spending and taxes in 10 weeks that has eluded Congress and the White House for years.

Finding the savings to pay for Obama’s package of tax cuts and infrastructure spending would mean broadening the committee’s deficit-reduction target by nearly a third.

Obama has promised that he will lay out a proposal Sept. 19 to help the committee meet its original mandate and pay for his job creation proposals.

The president said his deficit-reduction proposal will include spending cuts, modifications to Medicare and Medicaid, and tax increases for the wealthy and big corporations.

“We can reduce this deficit, pay down our debt and pay for this jobs plan in the process,” he told Thursday’s joint session of Congress. “But in order to do this, we have to decide what our priorities are.”

But in so doing, Obama injected his leading election-year legislative initiative into a fragile supercommittee process that will be dependent on a level of cooperation and goodwill that is uncommon in Congress today.

The panel opened its work this week striving for a different tone.

Sen. John F. Kerry (D-Mass.) told colleagues that their mission came from the American people, “who wonder if we still can — and desperately want us to — sit down like adults” and find agreement.

“My goal for this committee is to begin by seeking common ground,” Rep. Fred Upton (R-Mich.) told the group. “Surely, there are areas where we can agree.”

But after the president spoke Thursday, the hard-edged partisan rhetoric returned, as the panel’s Republicans criticized Obama for adding to the supercommittee’s responsibilities.

The panel’s Republican chairman, Rep. Jeb Hensarling (Tex.), said the proposal made the “already arduous challenge of finding bipartisan agreement on deficit reduction nearly impossible.”

Fellow committee member Sen. Patrick J. Toomey (R-Pa.) accused Obama of attempting to “pass the buck.”

The toughest critique came from Republicans who see key elements of the president’s plan as stimulus spending that they say is likely to add to the deficit without creating jobs.

Several had called for the committee to find more in savings than its $1.5 trillion legal mandate and were unenthusiastic at the prospect of starting the task with the budget in a deeper hole.

The president offered a spirited defense of his plan Friday in Richmond. Paying for it, he said, would not be difficult with a balanced approach that includes spending cuts and new tax revenue.

“Look, we spent a whole summer fussing about the deficit,” Obama said. “And it is legitimate for us to get a government that is living within its means, just like families do. . . . What I said last night is, let’s go further. Let’s be a little more ambitious.”

Some of the president’s Democratic allies, already anxious about assigning so much power to a handful of lawmakers working outside the normal legislative process, worry that the panel will sign on to a plan that cuts entitlement spending.

Under the adopted rules, members of Congress have limited options to halt a compromise they find undesirable. If the panel comes to an agreement, Congress must vote to accept or reject the recommendations; no amendments or filibusters are allowed.

Some Democrats who serve on the panel said they do not believe the president’s request has made their job harder. It could, in fact, make their task easier easier by spurring growth, which would mean higher tax collections and, therefore, a shrunken deficit, they say.

Easier, maybe, but surely not easy.

“In order for this committee to be successful, we’re not only going to have to be able to find common ground, but we’re going to have to make some hard compromises — and that was as true before the president’s speech as it was after,” said Rep. Chris Van Hollen (D-Md.). “This was always going to be complicated.”

Staff writer Felicia Sonmez contributed to this report.