Too Liberal? Too Conservative? Or Just Right?

Fascinating info graph showing the estimated ideological positions of US voters, senators, and representatives.

And here is is broken down by Red, Blue, and Purple:

So, we're much more centrist than our politicians would have you believe. What does that mean? Do we need the push pull of opposing ideologies to keep our legislation somewhere in the center? Or is it harder to sell moderates? Or are people who are drawn to politics just naturally ideologues?