Senator John McCain had intended to ride back into Washington on Thursday as a leader who had put aside presidential politics to help broker a solution to the financial crisis. Instead he found himself in the midst of a remarkable partisan showdown, lacking a clear public message for how to bring it to an end.

At the bipartisan White House meeting that Mr. McCain had called for a day earlier, he sat silently for more than 40 minutes, more observer than leader, and then offered only a vague sense of where he stood, said people in the meeting.

In subsequent television interviews, Mr. McCain suggested that he saw the bipartisan plan that came apart at the White House meeting as the proper basis for an eventual agreement, but he did not tip his hand as to whether he would give any support to the alternative put on the table by angry House Republicans, with whom he had met before going to the White House.

He said he was hopeful that a deal could be struck quickly and that he could then show up for his scheduled debate on Friday night against his Democratic rival in the presidential race, Senator Barack Obama. But there was no evidence that he was playing a major role in the frantic efforts on Capitol Hill to put a deal back together again.