Bringing an end to a long flirtation with a bid for the White House, Mayor Michael R. Bloomberg has officially closed the door on a presidential candidacy this year. In an Op-Ed article published in Thursday’s New York Times, Mr. Bloomberg wrote that he still believed that a nonpartisan approach was needed to solve the country’s problems and that an independent candidate could win. But he will not run, he said.

“I listened carefully to those who encouraged me to run, but I am not — and will not be — a candidate for president,” Mr. Bloomberg said. “I have watched this campaign unfold, and I am hopeful that the current campaigns can rise to the challenge by offering truly independent leadership. The most productive role that I can serve is to push them forward, by using the means at my disposal to promote a real and honest debate.”

In a switch, the mayor abandoned a promise to remain neutral and said he might work to help elect the right candidate.

“And while I have always said I am not running for president, the race is too important to sit on the sidelines, and so I have changed my mind in one area. If a candidate takes an independent, nonpartisan approach — and embraces practical solutions that challenge party orthodoxy — I’ll join others in helping that candidate win the White House.”

Mr. Bloomberg’s explanation for his decision came after months of careful denials that he was a candidate despite the elaborate behind-the-scenes effort to build the infrastructure of a campaign. Aides, under the guidance of Mr. Bloomberg’s political deputy, Kevin Sheekey, researched getting on the ballot in all 50 states, tested the mayor’s appeal across the country and made alliances from coast to coast. And he seemed to confirm that he would indeed run when he left the Republican Party in June 2007, paving the way for an independent campaign.

Read it here: Bloomberg Says He Won’t Run but Will Be Active