Marcus Morton played a significant role in the Massachusetts Constitutional Convention of 1853. He served as the president of the convention, which was convened to consider revisions to the Massachusetts Constitution. Morton's leadership was crucial in guiding the discussions and debates during the convention. The convention aimed to address various issues, including the structure of the state government and voting rights, although many of the proposed changes were ultimately rejected by the voters. Morton's involvement underscored his influence and prominence in Massachusetts politics during that period.