Hard to say what the effect will be, but reportedly, the day before the election, Rush Limbaugh has broken with precedent and, to all extents and purposes, endorsed a candidate in a Republican Primary:

Right after Rush finished the football segment, he popped in, out of reference or context, and read the best parts of the Human Events endorsement of Fred! I was sick in bed and heard it. He ended with asking the South Carolinians to seriously consider voting Fred Thompson if they believe in conservatism, and then went for the commercial.

Will it help? Hard to see how it can hurt.