Morning Buzz: March 28, 2008

Disgruntled by the negativity of his party's nominating contest, DNC Chair Howard Dean is asking Hillary Clinton and Barack Obama to do a better job of keeping their supporters from engaging in nasty exchanges. "You do not want to demoralize the base of the Democratic Party by having the Democrats attack each other," he told the Associated Press in an interview yesterday. "Let the media and the Republicans and the talking heads on cable television attack and carry on, fulminate at the mouth. The supporters should keep their mouths shut about this stuff on both sides because that is harmful to the potential victory of a Democrat."

Obama is set to receive the endorsement of Pennsylvania Sen. Bob Casey today. This move could help the Illinois senator make inroads among white working-class Pennsylvania voters, dubbed "Casey Democrats" because they tend to agree with Casey's opposition to abortion and support of gun rights. The endorsement comes as Obama begins a six-day tour across the Keystone State, which holds the next important primary on April 22. Clinton already has the endorsement of the state's popular governor, Ed Rendell.

The United States has begun providing air support to Iraqi forces in Basra, in southern Iraq, where security force ground troops have been engaged in combat with Shiite militias since Monday. U.S. warplanes conducted at least two airstrikes last night, according to reports.