For insights, the University of Pennsylvania's Annenberg Public Policy Center surveyed 13,800 people this winter.

It seems the vast majority of us say we neither know nor care which candidate has been approval-stamped by which newspaper, trade union, advocacy group or muckety-muck.

And when we do know and care, the net difference in support for the candidate tends to be paltry.

"When an endorsement does have an impact, in many cases, it will have a positive effect and a negative effect that cancel each other out," says Ken Winneg, director of the National Annenberg Election Survey, which was also conducted in 2000 and 2004.

Still, the data contain some telling stuff.

For example, while only 3 percent of us knew that National Right to Life endorsed Fred Thompson, the erstwhile Republican candidate, a whopping 73 percent were aware that Oprah Winfrey supports Barack Obama.

Unfortunately, Winneg says, the 2,375 people who knew of Winfrey's opinion were not asked whether it swayed them. This question about impact, added later, revealed that occasionally, a plug is a kiss of death.

The New York Times' endorsement of John McCain in the Republican primaries, for example, reduced his support among conservatives and very-conservatives by 10 percent.

The newspaper had anointed McCain as "the only Republican who promises to end the George Bush style of governing from and on behalf of a small, angry fringe."

- Marie McCullough