“This is a giant wake-up call,” said Terry McAuliffe, the former Democratic National Committee chairman who lost a bid for the Democratic nomination for governor in Virginia last year. “We have to keep our focus on job creation. Everything we have to do is related to job creation. We have to do a much better job on the message. People are confused on what this health care bill is going to do.”

David Axelrod, a senior adviser to Mr. Obama, said he did not view the results as a repudiation of the White House’s agenda — noting that Mr. Obama remains popular in Massachusetts — but acknowledged that the Democrats needed to do a more effective job of signaling concern about the problems gripping Americans today.

“We are the party in power and as such there’s an element of responsibility assigned,” he said. “I think people need to know that their challenges and their concerns are the focus of our work every day.”

“Senator Brown ran a really good race,” Mr. Axelrod said. “What he recognized is what we know and what we knew leading up to the election of 2008 and that is the middle class is getting slammed.”