The NYT has the scoop.
For an explanation of what the whole Rudy boomlet may have been about, check out the piece I wrote about Giuliani for New York magazine last month.
The Times story linked here mentions recent talk that Rudy could challenge incumbent Democratic Senator Kirsten Gillibrand. But I doubt it. From my NY mag story:
Even though a recent poll had Giuliani beating [Gillibrand] by nine points, Giuliani laughs off the idea. "My value is in running things," he told me. "Commenting is great, but I get to do that anyway on television and radio and [in] op-ed pieces." "It’s a job that we have discussed in the past, and he just has no desire to do it," [longtime advisor Anthony] Carbonetti says.