Then there’s Nathan Fletcher.

The former San Diego assemblyman went from being a GOP true-believer candidate for mayor in early March 2012 to an independent disdainful of both parties in late March 2012 to a Democrat who sang his new party’s praises in May of this year.

He was a devout GOPer when he was trying to win the party’s nomination for mayor. When the nomination went to Carl DeMaio, he became a devout both-parties-stink guy championed by The New York Times’ David Brooks. When that ploy failed and he finished a distant third in the June mayoral primary, Fletcher realized he couldn’t win as an independent and he couldn’t go back to the GOP. That left him pretty much no choice but to become a Democrat. The rapidity with which his political views changed simply make it impossible, a la Gramm or Chaffee, to see his shift as a principled evolution or as a reflection of the reality that national parties change as time goes by.

The politics of convenience may pay off grandly for this chameleon

Instead, Fletcher’s “evolution” seemed the epitome of the politics of convenience. (Or, to use a mid-20th-century reference, Fletcher seems like an affable political version of Sammy Glick.)

But incredibly enough, it seems to be working. As Democrats watch scandal-scarred San Diego Mayor Bob Filner flail away, many are beginning to think about who to back in a special election or a recall election.

There are obvious candidates — City Council President Todd Gloria; former state Sen. Christine Kehoe; former Assemblywoman Lori Saldana — who have long personal ties to Lorena Gonzalez, the local union kingpin who recently became an Assembly member. But by several accounts, Gonzalez is pushing hard for Fletcher.

As powerful as Gonzalez may be, however, it is hard to see Fletcher — a professed Ronald Reagan lover until 16 months ago — getting much institutional Democratic support.

So what would he need to overcome this antipathy? Money.

A Clinton ‘bundler’ — and Fletcher fan — in La Jolla

Which might be no problem for Nathan the Chameleon. This is from the San Diego Reader.

“Christine Forester, listed by Newsweek magazine as the nation’s second biggest “bundler” of contributions to the 2008 campaign of President Barack Obama, having collected more than $500,000 from a variety of friends and associates in that year alone, is spearheading a behind-the-scenes effort to draft newly minted Democrat and ex-GOP Assemblyman Nathan Fletcher for mayor if incumbent Bob Filner falters in his effort to remain in office.”

This is getting interesting. Especially since DeMaio’s emails the past few days sure seem like hints that he is considering another run for mayor instead of his expected  2014 House race against weak first-termer Scott Peters, D-San Diego.

Could we see DeMaio vs. Fletcher again? So soon?

Maybe.

But maybe we’ll also see more expedient party switching. Nathan Fletcher hopped around in a way that made Arlen Specter’s political rebranding seem saintly and tarnish-free — and apparently without consequence!