Some new details on the sexual harassment claim against Mayor Bob Filner. This story on News8 quotes Mesa College Political Science professor Carl Luna as thinking a recall is highly probable. Despite the gory details of the harassment claims, there is good reason for caution.
Petitioners would need over 100,000 signatures (15% of registered voters -- based on the last report, that number should be 100,808) in what is apparently 39 days (edit -- I thought it was 60, what is clearly poor drafting prevents signature gathering in the first 21 days after the recall is first published. I've never seen this mistake made, but it clearly has been here.).
100,000 valid signatures is a very high hurdle. In the US, I can think of four recalls that got on the ballot with a six-figure signature requirement -- Arizona Governor Evan Meacham in 1988 (he was impeached and convicted the day the recall was certified), Gray Davis in 2003, Wisconsin Governor Scott Walker and Lieutenant Governor Rebecca Kleefisch in 2012.
There have been others worth talking about. The recent attempt against Maricopa Sheriff Joe Arpaio needed 335,000 signatures. The proponents claimed they got 200,000, but didn't hand them in for inspection (as it wouldn't have mattered). The Miami-Dade mayoral recall of 2011 needed 52,000 signatures, and the Dianne Feinstein recall in 1983 as mayor of San Francisco needed less than 20K). The mayoral recalls in LA in the first half of the 20th century got closer to the requirement, but still don't top it.In 1938, 120,000 were handed in for the L.A. Mayor Frank Shaw recall, though the total needed was much less (I'm not sure the exact figure, though it may have been in the 60k range). The man who defeated Shaw, Fletcher Bowron also faced a recall in 1950, but the petitioners needed to get a little over 89,000 signatures.
This is not to say that petitioners can't get the signatures -- after all, California now has a well developed signature gathering industry. If someone starts putting some serious cash behind the recall, it is likely to start moving forward at an advance rate. Additionally, the disgust with Filner appears to be bi-partisan (though that may change if a recall would mean a Republican would likely be the replacement). However, history shows that 100,000 signatures in one city for a recall is a large challenge.