Indianapolis - Some Democrats are wondering why presidential candidate Barack Obama chose Delaware Senator Joe Biden for his running mate over Indiana Senator Evan Bayh.

Indiana University-Purdue University at Indianapolis political science professor Brian Vargus says Biden clearly has much more foreign policy and national security experience - an area that polls show Obama lagging in - than Bayh.

He also says Obama needs an "attack dog" - the sort of thing Bayh isn't known for.

Vargus says if Bayh continues to have eyes on the White House, he has to show himself as a more known and effective senator.

But state Democratic Chairman Dan Parker says the vice presidential selection process has given Bayh national exposure as a leader, and that's bound to enhance his reputation.