Sens. Evan Bayh (Ind.) and Joseph R. Biden Jr. (Del.) are also being seriously vetted by the campaign staff, according to sources with knowledge of the process.
Obama has revealed little about which way he is leaning. And despite rising anticipation that a decision is imminent, campaign officials said an announcement is likely in mid-August, shortly before the Democratic National Convention. Obama's top aides, David Plouffe and David Axelrod, huddled yesterday in the Washington office of Eric Holder, who along with Caroline Kennedy is vetting potential running mates.