The 1973 New Jersey State Senate Senate elections coincided with Brendan Byrne's victory in the gubernatorial election. Byrne's large margin of victory over Republican Charles W. Sandman, Jr.—he won by 721,378 votes (66.4%-31.1%) helped Democrats gain 13 seats in the State Senate, giving Democrats control, 29-10, with one Independent. Republicans were also not helped by a divisive primary that saw the incumbent, William Cahill, a moderate, lose to the more conservative Sandman. Cahill barely supported Sandman in the general election. This election marked the first time since 1967 that Democrats controlled the State Senate.