WASHINGTON (AP)  Supporters of a third-party presidential bid by Mayor Michael R. Bloomberg began a 50-state petition drive on Tuesday seeking to “draft” the mayor, a billionaire who is edging closer to entering the race while continuing to deny he is a candidate.

The petition effort was announced by two veteran political hands who say the current system in Washington is broken and needs a nonpartisan, pragmatic leader like Mr. Bloomberg.

Gerald Rafshoon, a former spokesman for President Jimmy Carter, and Doug Bailey, a longtime Republican consultant, are not the first to start an online petition drive for Mr. Bloomberg, but their move comes at the height of the primary season. They filed with the Federal Election Commission and the I.R.S. to start the draft-Bloomberg effort.

“He’d be a very unique candidate for a very unique time,” Mr. Rafshoon said.

Mr. Bloomberg, a 65-year-old Democrat-turned-Republican-turned-independent, continues to say that he is not a candidate, but he has been polling and conducting a voter analysis in every state as he decides whether to make a bid for president.