I lived in New York City during the heyday of Three-Card Monte. Walking down any street, at any time, you could not avoid shouts of “Pick a card, any card.”

Today’s political discussions evoke similar feelings. Everyone has a theory, a story to tell, and the proliferation of primary polls provides everyone with evidence “proving” his or her interpretation.

Say you want to argue that the controversy over Obama’s “bitter” comments had no impact on the Pennsylvania primary – you’ve got the data to back up that claim. On April 8, days before the comments, the InsiderAdvantage poll showed Hillary Clinton with a 10-point lead. On April 20, a week after the controversy erupted, Clinton’s lead was exactly the same 10 points. No impact.

Public Policy Polling might even allow you to argue that Obama’s sociological analysis helped him. Just before the comments, Clinton clung to a three-point lead, in their telling. Within days of the comments, Obama had turned it around and led by three.

However, let’s say you wanted to press the opposite claim – that Obama’s comments dealt a devastating blow to his Pennsylvania prospects. Just turn to ARG. The week before the comments surfaced, Clinton and Obama were tied, they say, but as the story broke she turned that into a 20-point blowout, which settled back to a 10-point victory.

So we have same-poll to same-poll comparisons telling us the “bitter” comments helped Obama and hurt him – and that they had no effect. Pick your story and you have the data to back it up.

What of the Rev. Wright controversy? In a story headlined “Polls show Barack Obama damaged by link to Reverend Jeremiah Wright,” the Times of London “proved” their contention by citing Gallup – “A new national Gallup tracking poll shows Hillary Clinton regaining her lead over Mr. Obama for the first time in a month, now leading 49 percent to 42 percent, a 13-point shift to the former First Lady in less than a fortnight.”

Under a different headline – “Wright Controversy Doesn’t Hurt Obama, Poll Shows” – The Wall Street Journal argued the opposite case from a different set of polls: “The [Pew] survey