What it takes to unite the Democratic Party.Broadcast: Midmorning, 08/27/2008, 7:06 p.m.St. Paul, Minn. ? Delegates to the Democratic National Convention began casting their votes for the party's presidential nominee today, in a process that remains a mystery. Staunch supporters of Hillary Clinton would like to see a roll call vote that polls every state. But some expect Clinton to ask her delegates to throw their support to presumptive nominee Barack Obama by acclamation. Political reporter Matt Bai says there's another issue that Democrats have to grapple with -- how race will figure into the general election. Guest: Matt Bai: Covers national politics for the New York Times Magazine. He's the author of "The Argument: Inside the Battle to Remake Democratic Politics."