WASHINGTON — In the span of a single week -- from the day Arlen Specter turned Democratic to the moment Congress passed the White House's budget blueprint and on through the opening of a spot on the Supreme Court -- President Obama crossed a fateful line: From now on, it's his country.
Every president inherits a tangle of problems from his predecessor. War and recession, natural disaster and foreign crises. And for some undefined interval, new presidents argue that they should not be accountable for the troubles that arose on another's watch.
But inevitably, responsibility shifts. And for Obama, that time came last week, bringing both greater opportunities and greater risks.
On the economy, Obama won approval Wednesday of a $3.5-trillion budget plan that aims to help pull the country out of the worst recession in decades. It also smooths the way for one of the president's signature domestic priorities -- overhauling the nation's healthcare system.
At the same time, the budget projects a whopping $1.2-trillion deficit in 2010, undercutting Obama's ability to bemoan Bush-era red ink.
"It is now absolutely his economy," said Paul Light, a New York University professor who specializes in presidential transitions. "I don't think that the public will continue to believe that this was all George W. Bush's doing. And every day that goes by, it becomes more Obama's than Bush's."
Ever since his inauguration, Obama has nurtured the idea that responsibility for grim economic conditions rested with former President Bush. As recently as Wednesday, Obama sought that political cover when it was announced that the economy had shrunk by 6.1% in the first quarter of the year.
Speaking at a town hall meeting near St. Louis, he said: "Now, we've got a lot of work to do, because on our first day in office we found challenges of unprecedented size and scope."
But the events of the last week made Bush seem less relevant, presidential experts and political strategists said. As Obama's imprint on the economy grows, so does his ownership of the issue.
That ownership became almost literal as Obama moved more deeply into the banking and auto industry crises.
As the Treasury Department finished "stress tests" on 19 of the country's biggest banks, the administration became further enmeshed in the workings of the financial system.
And on Thursday, Obama announced he was pushing Chrysler into bankruptcy. He may take another corporate icon, General Motors, down the same path.
As a kind of shareholder in chief, the president now is responsible for guiding companies with thousands of union workers and investors -- firms that remain vital to the economies of states that stretch across the nation's industrial heartland, from Pennsylvania to Illinois and south into Kentucky and Tennessee.
Though the auto industry was in crisis before Obama reached the White House, his team has been in charge of the rescue effort for the last four months.
"The perception will be that Barack Obama owns this bankruptcy," said Neil Newhouse, a Republican pollster. "He owns this economy."
On the political front, the decision by Pennsylvania's senior senator to join the Democrats moved Obama to the brink of a 60-vote majority in the Senate, which could prevent Republicans from blocking his initiatives by filibuster. One of the people instrumental in persuading Specter to abandon the GOP was Vice President Joe Biden, reinforcing the appearance of White House influence on Capitol Hill.
All that raised expectations that Obama should be able to win congressional approval of his core agenda.
Yet Specter insisted he would not be a rubber stamp for the president. He promptly voted against the Obama budget. And although Democrats have a strong majority in the House, their control of the Senate is still far from absolute.
Democrat Al Franken, the apparent victor in the still-contested Minnesota Senate race, has yet to be seated.
In addition, Obama must work to get support from such relatively conservative Democratic senators as Ben Nelson of Nebraska.
"It's nice to say you have 60 votes. Having said that, there are going to be tensions within the Democratic caucus," said Harold M. Ickes, deputy chief of staff under President Clinton.
As for the Supreme Court, David H. Souter's announcement Friday that he was stepping down gives Obama a chance to start putting his mark on the court, one of the most lasting elements in a president's legacy.
Souter has been a reliably liberal vote on the court. But Obama, if he chose, could come up with a replacement even more progressive and more inclined to uphold his policies, should they face legal challenges.
Or, seeking to reinforce his moderate image and avoid a potentially bruising confirmation battle with Senate Republicans, the president could choose someone with a more centrist record.