About a quarter (23%) of registered voters identify themselves as swing voters, according to a Pew Research Center survey conducted April 4-15. A swing voter is someone who is undecided, or leans to or favors a candidate but says there is still a chance he or she will change their mind.

This is a significantly smaller swing vote than was the case at the end of the primary season four years ago. In June 2008, 33% of all registered voters, and fully 46% of independent voters, remained uncommitted.

Past surveys show this is not uncommon when an incumbent is up for reelection and voters feel they have a clearer sense of the options before them. In June 2004, just 21% of registered voters were swing voters, including only 28% of independents.

Many independents have yet to commit to either Obama or Romney. While 90% of independents express a preference, only 66% say they are certain about how they will vote. Read More

Russell Heimlich  is a former web developer at Pew Research Center.