From a new Pew survey on the public's knowledge:

About half of Americans (53%) can correctly identify the Democrats as the party that has a majority in the U.S. House of Representatives. In February 2007, shortly after the Democrats gained control of the House after a dozen years of GOP rule, many more people (76%) knew the Democrats held the majority.

In 2004, voter turnout was 64 percent. That means there will be at the very least 20 million Americans heading to polls in November who don't know that the Democrats control the House. Sigh.