Trying to position himself as a candidate that independents could rally around as an alternative to the two parties, New York billionaire Mayor Michael Bloomberg has seen his aspirations for the presidency disappear over the last few days in the boom accompanying the candidacy of Barack Obama:

Mr. Obama has stressed that he wants to move beyond gridlocked politics and usher in an era of national unity. A key organizer of the effort to draft Mr. Bloomberg for a presidential run acknowledged in an interview on Monday that that Mr. Obama’s rise could be problematic.

“Obama is trying to reach out to independent voters, and that clearly would be the constituency that Mike Bloomberg would go after,” said Andrew MacRae, who heads the Washington chapter of Draft Mike Bloomberg for President 2008. “An Obama victory does not make it impossible, but it certainly makes it more difficult.”

The event was organized by former Senator Sam Nunn, Democrat of Georgia, with former Senator David L. Boren, Democrat of Oklahoma. In the days leading up the event here, just outside Oklahoma City, Mr. Boren suggested that he would encourage Mr. Bloomberg to run if the major party nominees failed to heed the call for bipartisanship.

But several leading participants took pains to say that they had no intention of abandoning their own parties in the election. Some even cast Mr. Obama’s success as evidence that the nation was yearning for the type of leadership they were offering.