As a member of the House Committee on Redistricting, Peña has been advocating for a Hidalgo-based congressional district. Peña knows that he probably wouldn't be able to foster enough support to beat out state Senator Eddie Lucio Jr. or his son, state Rep. Eddie Lucio III, in the primary race for the congressional seat. The Lucios are hometown favorites, but suffer from many of the same symptoms of South Texas Democrats. If Peña wants to keep moving up as a political figure, his best bet is to switch sides, taking some voters with him and gaining the support (and money) of Hidalgo Republicans. So you can see now why the Republican Party looks pretty sexy.
There is lots and lots of instructive data in Daniel Lucio's article so go read all of it. My point here is that there is simply no chance Pena remains a Democrat (as if he ever was) unless he plans on retiring from politics (no chance of this either).
He draws the new congressional district's boundaries in the coming legislative session, then runs for the seat in 2012. How can a scheming weasel like Peña resist?
Greg has more, and so does Harold Cook, who lays out a compelling combination of reasons disagreeing with my premise.
Update: Lucio's article appeared first at his blog, Speak South Texas.