Congress is becoming more partisan after every election. As current budget standoffs show, the two sides often cannot agree on a reasonable course of action. Voters should support more moderate candidate to ensure that the Congress can actually do its job, passing legislation. The current Congress has proved to be one of the least effective in history.
Yes, I am concerned that it does seem like moderates are being pushed out of Congress. The Republican party used to have a lot of varying viewpoints and it seemed like Republicans and Democrats could agree on more things in the past. Today, the Republican party seems to be dominated by extremists who are only concerned about a very narrow agenda.