As part of his standard stump speech, he explains his liberal past this way:
"Rudy is always the first to paraphrase Churchill when he echoes if you aren't a liberal in your 20s you have no heart, and if you aren't a conservative by your 40s you have no brain," said Giuliani's top adviser, Anthony Carbonetti.
However, according to the Churchill Centre, this is a complete fabrication:
There is no record of anyone hearing Churchill say this. Paul Addison of Edinburgh University makes this comment: "Surely Churchill can't have used the words attributed to him. He'd been a Conservative at 15 and a Liberal at 35! And would he have talked so disrespectfully of Clemmie, who is generally thought to have been a lifelong Liberal?"
Of course, the truth has never stopped Rudy before so why start now?