The registration numbers in CA-36 changed from a two point Republican advantage when the maps were first released, to a very narrow Democratic advantage by the time election day rolled around. The state democratic party created a powerful ground game in Riverside County from nothing and that brought out a lot more Hispanic voters. Plus, Bono Mack's attacks on Ruiz in the last month probably didn't help her crossover support, as preliminary results show that Ruiz crushed in Palm Springs. Obama also appears to have done a few points better in Palm Springs, as well as Coachella and Indio, while not losing much ground in other areas. The precinct maps for the congressional and presidential races are at these links
http://www.pe.com/local-news/politics/jim-miller-headlines/20121109-2012-election-obamas-support-dropped-in-inland-area.ecehttp://www.pe.com/local-news/politics/jeff-horseman-headlines/20121109-election-2012-ruiz-takes-seat-bono-mack-concedes.eceZoom in for better detail, it gives percentages for each precinct.