With McCain’s obvious decline in recent weeks, however, Graham may see the writing on the wall. His rants are out of desperation, as that giant sucking sound he hears is his Vice Presidency and very possibly his Senatorial career swishing around the opened drain.
He's also devoted a lot of effort to sucking-up to Hillary Clinton. It's possible she's dangled the possibility of the Attorney General post in her administration to entice him.
Graham seemed like a good guy during the impeachment process, when he was still in the House, but in recent years he has been weak...maybe the ‘Rats have some dirt on him they are using to blackmail him.