Why are Republicans trying to ban exit polls?

As you may have heard, Republicans in several states, notably Florida and Ohio, have tried to ban exit polling. Yesterday, a judge overturned the ban in Florida, and several days ago a judge in Ohio overturned the ban, but Secretary of State Ken Blackwell, Republican candidate for governor, issued confusing new orders that may well be interpreted by election authorities as banning the polls.

Also, as you know, Florida and Ohio vote almost exclusively on electronic machines, most of which have no paper trail and many of which were built by Republican controlled Diebold. Because there is no paper trail, the only conceivable check on vote fraud is the exit polls.

So, tell me, if the Republicans haven't got a "fix" going, why are they so interested in preventing exit polling?