A senate race in Massachusetts has revolved around the question of one of the candidates being "too old" for another term in office.

U.S. Rep. Seth Moulton, 47, a moderate Massachusetts Democrat, is challenging U.S. Sen. Edward Markey, who is 80 years old for the Democratic nomination in the senate race.

RELATED: Map: These states have approved redistricting plans to influence midterm elections Moulton is seeking to unseat Markey in the state's Democratic primary election on Tuesday, Sept. 1.