" On New Year’s Day, Hillary and Bill were out on a boat, bobbing along on the blue-green sea, and decided to take a swim. They leapt into the water, swam up to the beach, and then Hillary posed the question directly to the person who knew her best—and who understood as well as anyone alive what running for president entailed.

What should I do, Bill? she asked. Should I do this or not?

You have to ask yourself one question, he replied. Of all the people running, would I be the best president? If you can answer yes, then you need to run. If you’re not sure, then you need to think more about it, and if the answer is no, don’t do it. That’s all I can tell you, Bill said.

Not long after, Solis Doyle’s phone rang back in Washington.
“Bill said that if I really feel like I can do this, and do a good job
and be the best one, then I should do it,” Hillary said. “And I do
believe that.”

Solis Doyle exhaled and smiled.
“Okay! Let’s go, then!” Patti said, and they were finally off and running. "

― John Heilemann , Game Change: Obama and the Clintons, McCain and Palin, and the Race of a Lifetime