Complex sentence: The Iowa caucuses have historically been the first caucus held in the United States, marking the traditional formal start of the delegate selection process for the 2008 United States presidential election, and the process in which members of the Democratic political party gathered to make policy decisions.
Split into simpler sentences: The Iowa caucuses have historically been the first caucus held in the United States. The caucus marks the traditional formal start of the delegate selection process for the 2008 United States presidential election, and the process in which members of the Democratic political party gathered to make policy decisions.