Here are the key findings:

First, by a 90 percent to 8 percent margin, registered voters say that they already pretty much know what they need to know about President Obama.

Second, by a 69 percent to 28 percent margin, these voters say that they already pretty much know what they need to know about Romney. In other words, three times as many voters are still evaluating the presumptive GOP nominee as are evaluating the president.

Third, among independents — who are almost certainly the lion’s share of those who have not yet formed a strong opinion of Romney — 42 percent say they want to know more about his record as governor, 37 percent want to know more about his record as CEO of Bain Capital, and 35 percent want to know more about his tax returns. Just 21 percent of independents want to know more about his wealth, 19 percent want to know more about his family and upbringing, and 16 percent want to know more about his religious beliefs.

These findings go a long way toward explaining the 2012 contest. In the referendum model of the election, voters ask themselves two questions: First, do I want the president to be re-elected? Second, is the challenger so unacceptable that I simply can’t bring myself to vote for him?

The Pew poll suggests that the vast majority of voters are not carefully weighing the two choices, as the “choice” model would suggest. Instead, they have already made up their mind about the president. Given Obama’s persistent polling below 50 percent, especially among independents, we might surmise that it is a net negative verdict.

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