I see that the Second Amendment is a big deal with regards to the choice if you're voting R or D.
Anyway, besides their reform, previous legislatures records and voting records, IMO it is a good way to see which companies or groups are donating to a candidate's campaign funds.
Showing these clusters of contributions from people associated with particular organizations provides a valuable—and unique—way of understanding where a candidate is getting his or her financial support. Knowing those groups is also useful after the election, as issues come before Congress and the administration that may affect those organizations and their industries.