He was a dedicated conservationist who delivered the keynote address at MIT on the first Earth Day in 1970. He had earlier served as state commissioner of natural resources for ten years, and went on to win appointment as state Commissioner of Public Works in 1964.
He ran for Lieutenant Governor of Massachusetts with the slogan "Put Sarge in Charge" and was elected in 1966, and in 1969, he became governor when Governor John Volpe (R) became secretary of Transportation under President Richard Nixon. In 1970, Sargent won election in his own right, defeating Boston Mayor Kevin White.
When he first entered office, the budget was in turmoil because of spending increases on welfare and other benefits. He tightened rules for qualifying for Medicaid and introduced a new corporate tax.
According to Barney Frank's book The Story of America's Only Left-handed, Gay, Jewish Congressman by Stuart E. Weisberg, In the election of 1970, against Kevin White, White was the first mayor to declare the city had a race problem and that people did not want him to become governor and keep him as mayor. Frank said, "Sargent was seen as a good liberal and some liberals reasoned that if we elect Kevin White as governor, who knows who is going to be Mayor of Boston." Frank said it was Sargent's popularity that won him the election.
He was governor of the Commonwealth during the strife over school busing following Judge W. Arthur Garrity's 1974 decision to desegregate Boston public schools through court-mandated redistricting of the Boston school system, including busing some students out of their neighborhoods to end a pattern of racial segregation in the schools. Sargent had previously vetoed attempts to repeal or water-down the state's Racial Imbalance Act, which prohibited state aid to racially imbalanced school districts. When Sargent called for obeying the federal court order, anti-busing forces complained that he and his neighbors in the well-to-do suburban Boston town of Dover, Massachusetts did not have to share any of the burden of desegregating Boston schools. Carl Sheridan, a former Dover police chief, said this of the incident, "I think people will most remember him for the busing situation. I remember one time a bus load of demonstrators came out to Dover looking for Sargent and his house. But because the town had no street lights, they got out of the bus and were standing in the pitch black. They got back in the bus and left. Sargent was still laughing about that two weeks ago."
Other accomplishments of the Sargent administration were far reaching. Statewide laws protecting the environment and wetlands were instituted, and Sargent advocated the introduction of no-fault auto insurance.
Governor Sargent was very much a man of his time. He ordered the flag to half-mast in recognition of the student killings at Kent State, was the keynote speaker at the first Earth Day at MIT, and sponsored legislation challenging the legality of the war in Vietnam.
Sargent also created weekend prison furlough program. After the Massachusetts Supreme Judicial Court ruled that this right extended to first-degree murderers because the statute did not specifically exclude them, the Massachusetts legislature quickly passed a bill prohibiting furloughs for such inmates. However, in 1976, Michael Dukakis vetoed this bill. Willie Horton was released on June 6, 1986 for a weekend furlough, but did not return. On April 3, 1987 in Oxon Hill, Maryland, Horton twice raped a local woman after pistol-whipping, knifing, binding, and gagging her fiancé. He then stole the car belonging to the man he had assaulted. He was later captured by police after a chase. On October 20, Horton was sentenced in Maryland to two consecutive life terms plus 85 years. The sentencing judge, Vincent J. Femia, refused to return Horton to Massachusetts, saying, "I'm not prepared to take the chance that Mr. Horton might again be furloughed or otherwise released. This man should never draw a breath of free air again."
He also created the Massachusetts Appeals Court in 1972, and elected Alan M. Hale, who was a justice of the Superior Court at the time, along with David Rose, Edmund Keville, Reuben Goodman, Donald Grant, and Christopher Armstrong, and were sworn under oath in October 1972. Hale said of the experience, "I wasn't too darn anxious to come here. I liked what I was doing. I enjoyed the experience on the Superior Court, meeting people and lawyers all over the State. I didn't want to leave, but the challenge of setting up an entirely new court was one I could not refuse." The Governor went on to speak of Chief Justice Hale and his five associates, "I have sought individuals who have a proven record of outstanding legal accomplishment, wisdom and good judgment. It is my belief that the men we have selected will allow this court to take its rightful place in our judicial system. It is a bench both balanced and responsive. It will, from the outset, be able to shoulder its full share of an appellate overload which for many years has been staggering." Sargent called the creation of the Appeals Court "the single most significant step in judicial reform in Massachusetts this century."
He retired from politics after his defeat for reelection by Michael Dukakis in November 1974. He died in 1998 in Dover, Massachusetts, and is buried at the Highland Cemetery in Dover, Massachusetts.
He achieved renown among conservationists and advocates of a multi-modal urban transportation system by canceling most highway construction inside Route 128, with the exception of the Northern Expressway in 1970. Sargent became a strong advocate for changing the federal laws governing aid to states for highway construction so that more funds were available for mass transit projects such as subways and light-rail vehicles.
Frederick P. Salvucci, an engineer, said this of Sargent and the cancellation of the inner belt:
Yes, of course. In many ways the most thrilling moment in the history of the antihighway fight was when we won. And then Governor Sargent went on television and said, basically, he had been the public works commissioner who had fought for the inner belt earlier in his career and, as governor he said it was a mistake and "I'm going to admit that mistake and stop the program and we're going to shift towards public transportation." I mean it was thrilling. It was thrilling for us that had worked hard on it, but also, in fairness to Sargent how often do you see a public official who gets up and says, "I was wrong"? I mean it was an incredibly courageous thing for Frank Sargent to do, and I'm a Democrat. I don't say many good things about republicans. But he was a great man. I mean he had worked for this program. He always had an environmentalist bent to him. [A] lot of people do political analysis as to why he did this or that. I think he just believed what he said. "This was a mistake and we're going to go in a different direction." It was a thrilling moment in the history of it.
And then we actually moved in that new direction. I mean we shifted the funds, partly under Governor Sargent, partly under Governor Dukakis. Those monies that were going to go into destroying those neighborhoods or building the highways were shifted into refurbishing the commuter rail system, extending the Red Line, relocating the Orange Line, basically rebuilding the public transportation infrastructure of the city. That came out of that decision and another component of the same decision – you can go check that speech that Frank Sargent gave – was that the only highways that would continue to be studied within Route 128 would be the depression and widening of the Central Artery and the extension of I-90 over to Logan in an additional tunnel, the two components that are today called the Big Dig. Those were really part of that, if you will, anti-highway – "anti-highway's" probably the wrong name – pro-city decision that was made by Frank Sargent to shift towards a transportation strategy that would build the city instead of destroying it.
Sargent also called in Alan A. Altshuler, a political science professor at MIT take a new look at where we were headed in transportation policy. Sargent made him Secretary of Transportation and he presided over the Boston Transportation Planning Review. This review basically led to the stopping of the inner belt and the southwest expressway. Frederick P. Salvucci called them "two major very destructive interstate highways". But, the funds were reallocated towards public transportation, and saw the extension of the Red Line to Braintree and the relocation of the Orange Line.
While at MIT, he became a member of the Number Six Club, also known as the Tau Chapter of Delta Psi. Francis W. Sargent married Jessie Fay Sargent in 1938. She wrote a memoir in 1973 about their time in office, entitled The Governor's Wife: A View from Within. She helped to launch the Doric Dame, a group of volunteers that led tours of the Massachusetts State House. Jessie died on August 15, 2008, peacefully in her sleep. They have a son, Bill Sargent of Ipswich and two daughters, Fay of Acton and Jay of Middletown, Rhode Island.
Sargent's son, Francis W. "Bill" Sargent, Jr. was a candidate for the United States House of Representatives seat in Massachusetts's 10th congressional district in 1996. He lost the Republican nomination to Edward B. Teague III. In 1978 Sargent, Jr. was considered by the State Republican Committee to succeed William A. Casey as the Republican nominee for Massachusetts State Auditor after Casey dropped out to support Democrat Edward J. King in the Governor's race.