Voters head to the polls for primaries in six states today, with those in Arizona, North Dakota and Virginia inundated with the most money from super PACs trying to influence their votes. Here's a rundown of what outside groups are spending in the Grand Canyon, Peace Garden, and Old Dominion states, according to Sunlight's Follow the Unlimited Money tracker: 

Special Election: Arizona's 8th Congressional District

Among today's races, the special election to fill the remaining term of Rep. Gabrielle Giffords, D-Ariz., who resigned in January to focus on her rehabiliation, has attracted the most outside money ...