Inthemiddle is right that the republicans do a much better job of fear mongering and spreading lies, because of the fact GOP voters are less intelligent and with that far more easily to be misled.
Are you kidding me? You're really making yourself out to be completely ignorant here. First of all, "GOP voters" don't have to be led, or misled, into voting Republican. THEY'RE ALREADY GOING TO VOTE REPUBLICAN! The GOP base is going to vote the party ticket no matter what. Reagan could have been caught fucking a Soviet mule under date rape, and the "GOP voters" would have still supported him just the same as the "Democratic voters" rallied behind Clinton. Winning elections is about convincing the UNAFFILIATED and UNDECIDED voters. The people who will go either which way because they don't care about the party so much as the particular candidate. I'm sure you've forgotten, but there's a whole armada of us out here in this country who still refuse to view the world in terms of cookie cutters.
Second, there are plenty of intelligent people who are religious supporters of the GOP. When do you think was the last time that George Will, for instance, voted for a Democrat? How about Mary Madalin? Two very intelligent people right there who, no doubt, vote a straight GOP ticket every single time.
Third, and finally, stupid people can often times be very difficult to mislead, often times more difficult than intelligent people. You know why? Because stupid people are unpredictable! You never know what they're going to come up with out of left field. At least with smart people you can usually reasonably predict the things they're likely to consider. But try lying to a stupid person to sell them a bill of goods and most of the time you'll end up with "Well wait a second, I don't think I really believe you, because back in the days of JFK, there was the whole grassy knoell...." and all you'll be able to think is "WTF does that have to do with whether my magical elixir will make your penis grow?!?"