Pollster Scott Rasmussen notes that when he surveys head-to-head matchups between Hillary Clinton and any of the eight potential GOP candidates, Mrs. Clinton scores between 46% and 49% against all of them.

"When we polled her against Rep. Ron Paul, a non-mainstream libertarian, she got 48% of the vote. When we polled on Ron Paul among people who knew who Ron Paul is, she got 48% of the vote. When we polled among people who didn't know who Ron Paul is, she got 48% of the vote," he says.