The National Rifle Association primarily affects voting by making campaign contributions to certain politicians, while withholding them from others. The NRA also maintains a large and powerful lobbying interest in Washington, D.C. and in many state governments.
The primary way the NRA advances its goals is by donating money to the campaigns of politicians hostile toward gun control. While the NRA makes donations to politicians from both major political parties in the United States, the organization historically donates far greater amounts of money to Republican candidates. In the period between 1990 and 2012, for example, the NRA donated over $4 million to Republican candidates, while contributions to Democratic candidates totaled less than half a million, states the Washington Post. This pattern of contributions makes political sense, as Republican politicians are historically friendlier to gun rights than their colleagues in the Democratic party.
The NRA uses a politician's voting record, along with a questionnaire the organization produces, to determine how friendly or hostile that politician is toward gun rights. This system is similar to the grading system used in schools, with politicians garnering an A+ rating being champions of gun rights, while those with F ratings are typically impassioned advocates for stricter gun control laws. A "Q" is a special rating for junior members of Congress who respond favorably to the questionnaire, but lack a voting record on gun-control legislation.