Fantastic tick-tock from ABC's Jan Crawford Greenburg

It wasn't until Sunday night that John McCain, after meeting with his four top advisers, finally decided he could not tap independent Sen. Joe Lieberman of Connecticut to be his running mate. One adviser, tasked with taking the temperature of the conservative base, had strongly made the case to McCain that it would be a disaster for the party and that the base would revolt. McCain concluded he could not go that route. The next day, McCain studied the three men at the top of his shortlist: Minnesota Gov. Tim Pawlenty, former Massachusetts Gov. Mitt Romney and former Pennsylvania Gov. Tom Ridge. All had different strengths and negatives, but McCain was not satisfied. None of them had what McCain believed he needed to do -- and would have done -- with Lieberman. McCain wanted to shake up the ticket. Alaska Gov. Sarah Palin's name was in the mix as an unconventional choice for months, but she had not been considered a front-runner. So, over the next few days, with McCain continuing to believe he needed someone who had more of a maverick streak than his other choices, lawyers reviewed her vetting information. They kept their activities from even some in McCain's most senior inner circle.... The campaign secretly flew Palin into Dayton last night. She and McCain met privately for a couple of hours. McCain concluded she would "shake up the system" and was "a maverick," qualities he believed Lieberman would have brought to the ticket. But she also would appeal to conservatives -- which Lieberman most certainly would not have done. After their meeting, McCain concluded he was comfortable with his choice. He notified Pawlenty this morning that he was going in a different direction.