Somewhere along the way, the apostle of change became its target, engulfed by the same currents that swept him to the White House two years ago. Now, President Obama must find a way to recalibrate with nothing less than his presidency on the line.

The verdict delivered by voters on Tuesday effectively put an end to his transformational ambitions and left him searching for a way forward with a more circumscribed horizon of possibilities. Facing a hostile House with subpoena power and a diminished majority in the Senate, he will have to figure out the right blend of conciliation and confrontation to reassert authority and avoid defeat in 2012.

The most pressing question as Mr. Obama picks through the results on Wednesday morning will be what lessons he takes from the electoral reversals. Was this the natural and unavoidable backlash in a time of historic economic distress, or was it a repudiation of a big-spending activist government? Was it primarily a failure of communications as the White House has suggested lately, or was it a fundamental disconnect with the values and priorities of the American public?

“He will read the results carefully and hear the messages the American people are sending,” David Axelrod, the president’s senior adviser, said in an interview. “I think he’ll do that with care and with humility. But he’s also very centered, and his impulse is to focus on what we do next and how we respond in a way that’s constructive.”