Luke Ravenstahl's early start on his re-election bid is a call to action for a strong, single challenger with the experience, know-how and heft to take him on.

The mayor, who lucked into the job, fumbled early in his tenure and displayed all-too-infrequent moments of promise, has seemed to operate on autopilot for much of the last year. With the announcement that he's holding a $500-a-plate fundraiser next month, though, he put to rest any speculation that he's lost interest in another four-year term.

The question is why he thinks he deserves one.

With the primary election for mayor of Pittsburgh almost two years away, in 2013, Mr. Ravenstahl is making an early play for support, which may be a smart political move on his part. But the advance warning of his intention to run also puts the heat on potential challengers to get their acts together.

Although there hasn't been a peep out of city Republicans, who have failed to field a formidable candidate in the mayoral race for decades, a raft of Democratic possibilities has been mentioned. City Controller Michael Lamb and Councilman Bill Peduto have been laying the groundwork for runs, outgoing Pennsylvania Auditor General Jack Wagner has said he's "giving it a lot of thought" and outgoing Allegheny County Executive Dan Onorato may be considering it.

The best outcome for Mr. Ravenstahl would be a Democratic primary with multiple challengers, so that his opponents divide the anti-Luke vote, enabling him to cruise to nomination and, ultimately, re-election. Soon enough, the entrenched young Ravenstahl could be mayor-for-life. So this is no time for contenders to sit on their hands or engage in a contest of wills among themselves.

Would-be Democratic candidates who are truly interested in the betterment of the city must put aside their personal aspirations and join forces to put up a single opponent who will be a forceful leader, sound fiscal manager, strong partner with state and federal officials and a smart voice among corporate and philanthropic powers. In short, the kind of mayor Pittsburgh has been lacking for five years.

It's bad enough that the mayoral election season now will rival the presidential campaign in length. It will be worse if the time is wasted.