Democrat Tom Carper says Obama has picked a running mate who - as an expert in foreign policy - "brings strength to the ticket in an area where it is most needed."
Carper says he's known Senator Joe Biden for more than 30 years. They've been in the Senate together for eight years.
Carper calls Biden, "a principled and experienced legislator, a tough negotiator, a gifted orator, an enthusiastic campaigner, and a good and decent human being."
Obama announced his pick early Saturday with a message on his Web site and by sending text messages to supporters.
Obama and Biden plan their debut Saturday afternoon outside the Old State Capitol in Springfield, Illinois.
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