Busy day.

Mitt Romney had a good night. He won Wisconsin, Maryland and Washington DC. Romney is noticeably turning his oratorical firepower on President Obama.. and beginning to ignore Rick Santorum, Newt Gingrich and Ron Paul. President Obama is returning the favor.. now attacking Mitt Romney by name.. feels like the campaign is beginning in earnest. Rick Santorum's campaign is acknowledging they need to win his home state of Pennsylvania on April 24th to continue waging a campaign for the nomination.

President Obama today signs a new bill that makes it illegal for members of Congress, the President and thousands of federal workers to do insider trading.

1155EDT -- POTUS signs the Stop Trading on Congressional Knowledge (STOCK) Act, which makes clear that Members of Congress are subject to the same insider trading laws that apply to everyone else. VPOTUS also attends. South Court Auditorium. LIVE

...CANDIDATES

NEWT GINGRICH

1530EDT -- Holds rally at the Univ of NC Wilmington, Wilmington, NC. ABC TAPE

RON PAUL

2330EDT -- Holds town hall at UCLA, Los Angeles, CA.

MITT ROMNEY

1200EDT -- Addresses the American Society of News Editors Convention at the Washington Marriott Wardman Park, Washington, DC. CSPAN LIVE

RICK SANTORUM

1130EDT -- Holds press conference focused on energy development at Sheetz, Irwin, PA. LIVE via LiveU

Another day of extreme weather on the agenda. Keep a close eye on the lower Mississippi Valley all the way to the Mid-Atlantic.. from New Orleans to Tallahassee. Yesterday's dramatic twisters in Dallas-Fort Worth left more than 600 homes damaged. More than 10,000 remain without power. We'll be following developments closely.

There is a huge drama developing over the comments President Obama made about the Supreme Court's arguments over his health care overhaul. An appeals court now demanding the Justice Department tell them if the President believes the courts have the constitutional power to overturn federal laws.. or not. It's becoming quite a brouhaha. We'll ask several guests about it today.