After crisscrossing the country for weeks pushing his jobs plan directly to the American people, President Obama turned his attention to congressional Republicans on Thursday, promising to target them in 2012 if they stand in the way of his economic agenda.

“If Congress does something, then I can’t run against a do-nothing Congress,” Obama said in response to a question at a morning news conference. “If Congress does nothing, then it’s not a matter of me running against them. I think the American people will run them out of town, because they are frustrated, and they know we need to do something big and something bold.”

With his confrontational news conference at the White House, Obama brought back to Washington the fiscal debate that has been the source of bruising political warfare and left the American public disillusioned with their elected leaders during the economic crisis.

The president urged passage of the $447 billion American Jobs Act and warned Republicans who oppose the measure that they will have to explain their opposition “to me, and more importantly, to their constituencies” at a time of mounting economic uncertainty. He also endorsed a proposal from Senate Democrats for a surtax on incomes of more than $1 million a year to fund the jobs package, an idea that has already drawn opposition from the GOP.

Since unveiling the jobs package last month in a speech to Congress, Obama has touted provisions of it in appearances at schools, bridges and factories in eight states, most of them electoral swing states and some in GOP territory. On Thursday, the president spent most of the 73-minute news conference — just four minutes shy of the longest of his tenure — promoting the plan from a lectern in the august East Room.

As he has in his more feisty and partisan appearances outside the Beltway, Obama sought to highlight what he believes is Republican recalcitrance and the GOP’s role in the slowness of the economic recovery. He emphasized the support that elements of the proposal have received from both parties in the past. But the president also issued an explicit warning to Republicans that he would make any no vote a political issue in the emerging 2012 campaign.

“It’s fair to say that I have gone out of my way in every instance — sometimes at my own political peril and to the frustration of Democrats — to work with Republicans to find common ground to move this country forward,” Obama said. “Each time, what we’ve seen is games-playing, a preference to try to score political points rather than actually get something done.”

Despite Obama’s populist calls on the road for Congress to “pass this bill,” neither the Democrat-led Senate nor the Republican-controlled House has held a vote on the legislation.

The president vowed that if Congress does not approve the legislation as a package, he would seek to present the elements individually and demand an explanation for Republican opposition to each.

The warning represented one aspect of Obama’s emerging reelection message: That while he has worked to improve the economy, the Republican opposition has chosen a strategy focused on denying him a second term rather than putting the country back to work.

Republicans have countered that Obama’s government-centric approach to stimulating the economy is the wrong one during difficult economic times. The jobs proposal includes investments in education and transportation infrastructure, as well as tax cuts for small business owners that Republicans have said they might consider independent of the new spending provisions.

As Obama spoke, House Speaker John A. Boehner (R-Ohio) accused him of using the jobs plan as a campaign vehicle, telling an audience in Washington that “nothing has disappointed me more than what has happened in the last five weeks.”

“To watch the president of the United States give up on governing, give up on leading and just spend time campaigning,” Boehner said at the Washington Ideas Forum, an event sponsored by the Atlantic magazine. “We’re legislating. He’s campaigning. It’s very disappointing.”

Obama spoke of “the dings and bruises” he has suffered as a result of some of the steps he has taken since taking office in the hopes of pulling the country from a deep recession. A Washington Post-ABC News poll published this week found that four in 10 Americans “strongly” disapprove of the way Obama has managed the presidency. The poll also found that only 58 percent of Democrats believe Obama will be reelected.

Obama cited the damage to the American recovery caused by Europe’s fiscal turmoil, Japan’s devastating tsunami and the higher oil prices that have resulted from the Arab Spring. He also said the “debacle” of this summer’s partisan fight over how to raise the debt ceiling damaged the recovery.

“There is no doubt the economy is weaker now than it was at the beginning of the year,” he said.

But time and again he returned to his primary adversaries.

In what he called a “homework assignment,” Obama said near the end of the briefing: “Go ask the Republicans what their jobs plan is if they’re opposed to the American Jobs Act.”