Since the 80s political scientists have pointed to the 'myth of the independent voter'. It's been covered in most basic college poli-sci texts since that time.
Most data seems to indicate that of the electorate, only 10-11% of self proclaimed independents are truly independent. This is from Pew, Gallup, ANES studies/polls. Most independents are 'leaners' that fall in along dem/GOP party lines, rivalling the support of self proclaimed partisans.
The number of people who are not registering as a member of a party is increasing, but truly independent voters are much rarer.
Partisan shares the same root word as party for a reason. You have to belong to or support a party to be a partisan.
In politics, a partisan is a committed member of a political party. In multi-party systems, the term is used for politicians who strongly support their party's policies and are reluctant to compromise with their political opponents.
