The majority of Democratic voters in the US state of South Carolina believe that individual states, not Congress, should decide whether to allow online gambling and how it should be regulated.

South Carolina residents went to the polls earlier this week to vote for candidates running for office, and were also asked five non-binding referendum questions.

Republicans received two questions relating to a proposed ban on abortions in the state and whether state income tax should be phased out completely.

Democrat voters, meanwhile, were asked whether states, not Congress, should decide whether to allow online gambling and how to regulate it, with 72 per cent of voters agreeing.

Democratic voters also believed, by a 75 per cent majority, that the state should legalist gambling in order to raise new revenue to fund repairment work for roads and bridges, while 81 per cent favoured allowing the use of medical marijuana for people with chronic severe illnesses documented by a doctor.

Senator Lindsey Graham dismissed six tea party challengers to secure his GOP primary victory in the state on Tuesday. Graham is the author of a recently introduced federal bill to restore the long-standing policy that the Wire Act prohibits all forms of internet gambling.