Born in Deweyville, Texas, Leggett attended Southern University in Baton Rouge, Louisiana and, after serving in the Vietnam War with the U.S. Army, earned a J.D.

For two years, Leggett served as the chairman of the Maryland Democratic Party before leaving that position to run for office once again.

In his time as an undergraduate, he was a student leader in the civil rights movement and twice met Martin Luther King Jr.

He led the on-campus civil rights movement while at the same time commanding the Southern University Reserve Officers' Training Corps (ROTC) unit.

He was widely viewed as a potential running mate for Democratic nominee Kathleen Kennedy Townsend in that year's gubernatorial race.

When his term on the council was completed in December of that year, Leggett was elected as chairman of the Maryland Democratic Party.

In December 2004, Leggett left his position as Chair of the Maryland Democratic Party to begin a campaign to replace Duncan as Montgomery County Executive.

[5][6] He then faced Republican nominee Chuck Floyd and independent anti-tax advocate Robin Ficker in the general election.

Leggett dealt with the major local issue of a hiring site for day laborers from the city of Gaithersburg and the surrounding upper county area.

During the term of Leggett's predecessor Doug Duncan, Gaithersburg had struggled to find space within the city limits that the county could lease for use as a location where the day laborers could wait for employers.

In the fall general election Leggett defeated the Republican candidate James Shalleck by 65-35 percent, winning 212 of 245 voting precincts.

[5] Leggett and his wife are longtime philanthropic supporters of Montgomery College, with Catherine receiving an honorary degree in 2019.