During Briggs' time as governor, abolitionist activists continued to make inroads against both the Whigs and Democrats, primarily making common cause with the Democrats against the dominant Whigs. Briggs' stance as a Cotton Whig put him in opposition to these forces. He opposed the Mexican–American War, but acceded to federal demands that the states assist in raising troops for the war, earning the wrath of activist Wendell Phillips. He did promote other types of reform, supporting Horace Mann in his activities to improve education in the state.