I refer you to the Presidential election of 2008. Actually, there are many more, voters do this all the time. Go figure.
There is no comparison between 2008 and the Akin race. Obama won by 10 million votes. The Stupid Party nominated Maverick McCain who supported amnesty, cap and trade, regulating political free speech, etc. Obama was the unknown quantity. The choice was between Obama or a third term of Bush. The reality was that no Rep would have beaten Obama or Hillary in 2008. The economy was tanking, the public was fed up with war, and there was no way that most of the people were going to vote for the oldest man ever to run for the first time for the Presidency. And don’t forget what happened in the 2006 midterms—a sweeping victory for the Dems that put them back again in control of Congress.