GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) holds a baby during a visit to the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL)(R) and former Virginia Gov. Mark R. Warner exit together after a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) purchases a bag of peaches during a visit to the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL)(C) and former Virginia Gov. Mark R. Warner (R) greet people during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) samples a piece of peach before buying some during a visit to the Greensboro Farmers Curb Maraket August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) talks to people during a visit to the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL)(R) and former Virginia Gov. Mark R. Warner shake hands as they are introduced during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) listens as former Virginia Gov. Mark R. Warner introduces him to speak during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) holds a sunflower during a visit to the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) hugs Virginia Gov. Mark R. Warner after being introduced by him to speak during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) carries bags of fruit and corn as he visits the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) listens as former Virginia Gov. Mark R. Warner introduces him to speak during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) samples a piece of peach before buying some during a visit to the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) waits to speak during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) greets people after a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Former Virginia Gov. Mark R. Warner (seated) listens as presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) speaks during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC- AUGUST 20: People greet presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) during a visit to the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) speaks during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

GREENSBORO, NC - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) pays for corn he bought during a visit to the Greensboro Farmers Curb Market August 20, 2008 in Greensboro, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) greets people after a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) greets people after a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

RALEIGH, NC - AUGUST 20: Supporters of presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) show their support for him as he leaves his hotel August 20, 2008 in Raleigh, North Carolina. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Former Virginia Gov. Mark R. Warner (seated) listens as presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) speaks during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)

MARTINSVILLE, VA - AUGUST 20: Presumptive Democratic Presidential candidate U.S. Sen. Barack Obama (D-IL) waits to speak during a campaign event at the Patrick Henry Community College August 20, 2008 in Martinsville, Virginia. Obama is expected to announce his Vice Presidential candidate before the start of the Democratic National Convention on August 25th. (Photo by Joe Raedle/Getty Images)