*THE BLOGOSPHERE REACTS: Arlen Specter (R-PA D-PA), facing a strong 2010 primary push from Republican congressman Pat Toomey, switches parties, giving the Dems a quasi-60-seat presence in the Senate. This has the 'sphere all riled up. For some spirited commentary, visit Robert Stacey McCain's  blog ("Specter reminds me of the high-school slut trying to sleep [...]