Larry J. Sabato, political scientist at the University of Virginia, thinks Graham could be a formidable contender.
"He can raise a lot of money, and he can call upon his southern roots to argue that the Democrats need that kind of geographical balance on the ticket," Sabato said.
"He's obviously not a frontrunner, but he has to be taken seriously — he's not facing a field of candidates that is full of giants.
Certainly, he doesn't have much charisma, but he could be the anti-charisma candidate."