Nice idea. All this information is available to the public already, but I don't know how easy it is to access it in a user-friendly format.

Good Idea, There are a number of sites, starting with the official US Senate site, e.g. http://www.senate.gov/pagelayout/legislative/a_three_sections_with_teasers/votes.htm

and others found via Goggle Search "voting records", but there are 2 problems that I see:

1) Most of the sites that rate the politicians have their own agenda, e.g. http://www.aflcio.org/issuespolitics/votes/vr_memb.cfm and so the "grade" is based on a selection that they choose.

2) A challenger will have no record, and thus how does one compare them to a person in office.

My add on recommendation is that there be a site that records all votes, and also hosts profiles. That way a user could either pick up a specific profile, weight several profiles, or develop one of their own, and see how various politicians rated. A challenger would then be able to see which factors were important and could post how they would have voted and their ratings could then also be included.

Note: I have not yet found this site, but am trying to gather a list of interesting political sites at: http://www.wematter.com/Links.htm#billinfo

Just go to http://www.congress.org/ -- you can find everything you need there and/or can sign up for their 'Megavote' e-mails that come pretty much weekly and tell you what your Representative and Senators have been voting on, and how.