Don't understand how you can say that. Each party clearly refers to their "base" that part of the electorate will vote that party, just like Libertarians vote Libertarian. The election revolves around those in the camp of "undecided" "In an election, there are "certain" or "lock" votes - voters who are solidly behind or partisan to a particular candidate and will not consider changing their minds whatever the opposition says.
Swing voters are undecided about how they will vote. They are sometimes referred to as undecideds or undecided voters, but floating voter is now the more common term used for this kind of voter.
In the United States, they may be dissatisfied Republicans or Democrats who are open to the idea of voting for other parties, or they could be people who have never had a strong affiliation with any political party, and will vote depending on certain things that influence them - e.g. healthcare, benefits, election campaign etc.
Some might be people who have never exercised their right to vote before, such as those just reaching voting age.
Because the votes of swing voters are considered to be "up for grabs", candidates direct a fair proportion of campaign effort towards them, although they must also be concerned with voter turnout among their political base."
"updated 11:06 a.m. CT, Wed., Sept. 24, 2008
WASHINGTON - Nearly a fifth of U.S. voters remain undecided about presidential candidates Barack Obama and John McCain, still unsure which man can put out the fire raging through the American financial marketplace and save them from an economic meltdown."
It is clear that this block of voters exists and is the focus of political campaigns.