President Barack Obama kicks off his 100th day in office

President Barack Obama kicks off his 100th day in office with a new Democratic ally at his side.

Sen. Arlen Specter will discuss his new Democratic allegiance during an address with Obama and Vice President Joe Biden Wednesday morning. Specter ditched his Republican party designation of nearly 30 years Tuesday, saying he has found himself "increasingly at odds with the Republican philosophy," and declared himself a Democrat. The White House says Obama would campaign for Specter, who's up for re-election next year.

Later, the president is off to Missouri, where he'll hold a town hall meeting at a high school in the St. Louis suburb of Arnold.

Wednesday night, Obama holds a prime-time news conference.