As fears of a flu pandemic sweep across the globe, we get the very latest on what our government is doing to stop the spread of the disease in this country from the three top officials charged with coordinating our national response: newly sworn-in HHS Sec. Kathleen Sebelius, DHS Sec. Janet Napolitano, and CDC Acting Dir. Dr. Richard Besser. Plus, in his first television interview since announcing his unexpected switch to the Democratic party, Sen. Arlen Specter (D-PA) joins us live to discuss why he's leaving the Republican party after 5 terms in the Senate. How will his decision impact the Senate and the Democratic agenda? And will it help him save his hotly-contested Senate seat? Then, the future of the Republican party with: MSNBC's Fmr. Rep. Joe Scarborough (R-FL) & Fmr. RNC Chair Ed Gillespie.