Complex sentence: Independents may hold a centrist viewpoint between those of major political parties or a viewpoint more extreme than any major party, or they may have a viewpoint based on issues that they do not feel that any major party addresses.
Split into simpler sentences: Independents may hold a centrist viewpoint between those of major political parties. Sometimes they hold a viewpoint more extreme than any major party, or they may have a viewpoint based on issues that they do not feel that any major party addresses.