WASHINGTON (Reuters) - Former U.S. Senator Birch Bayh, who authored a landmark 1972 law mandating equal opportunities for women in education and sports and wrote constitutional amendments on lowering the voting age and presidential disability, died on Thursday at the age of 91.

Bayh, a liberal Democrat from Indiana, died of pneumonia, according to a statement from his family published by local media.

Indiana Governor Eric Holcomb described Bayh as a trailblazer who dedicated himself to improving the lives of everyone in the Midwestern state.

“His remarkable legislative and personal legacy transformed the country and will live on for years to come,” Holcomb said in a statement. “I ask Hoosiers around the state to join me and Janet in honoring his incredible service and by keeping the Bayh family in your thoughts and prayers,” he said, using a nickname for Indianans.

Bayh served in the U.S. Senate from 1963 to 1981. He was beaten in his bid for a fourth six-year term by future Vice President Dan Quayle in the conservative political tsunami that carried Republican Ronald Reagan to the White House in the November 1980 elections.

With a remarkable record of achievement in the Senate, Bayh is best known as “the father of Title IX” - the measure that barred sex discrimination in schools in both academics and athletics. It led to a revolution in sports as girls and women were given athletic opportunities in high schools and colleges that in many places had previously existed only for males.

“I thought that of all the areas of discrimination against women, the thing that had the greatest detrimental impact was not letting them have an education. If you give an education to a man or woman, or to a boy or girl, they have the freedom to do what they want in life,” Bayh told the Indianapolis Star in 2012.

Bayh was the first man since the United States’ 18th-century founding fathers to author two ratified amendments to the Constitution.

The 26th Amendment, proposed and speedily ratified in 1971, lowered the U.S. voting age from 21 to 18. It was adopted during the Vietnam War era amid criticism that it was incongruous for a nation to deem 18-year-olds too young to cast ballots but old enough to be drafted into war.

The 25th Amendment, proposed in 1965 and ratified in 1967, came in the wake of the 1963 assassination of President John Kennedy and the serious illnesses suffered in office by his predecessor, President Dwight Eisenhower.

It set out an orderly transition of power in the event of the death or disability of a president, and spelled out a method for choosing a vice president when a vacancy occurs in that office. It guided the procedures used after the resignations of Vice President Spiro Agnew in 1973 in a corruption scandal and President Richard Nixon in 1974 in the Watergate scandal.

It also provided the procedures for passing presidential responsibilities temporarily to the vice president, as Reagan did with Vice President George H.W. Bush after undergoing surgery in the 1980s.

Before Title IX, girls and women were routinely denied equal opportunities under the law in academics and sports - often blocked from medical and law schools and engineering programs and largely ignored in organized athletics.

The ascent of women and girls in all academic disciplines and in participation in scholastic and collegiate sports since 1972 - all the way to the many female American Olympic champions - stems directly from the simple, one-sentence measure.

TWO MORE AMENDMENTS

Bayh championed two more constitutional amendments that fell short. The Equal Rights Amendment - a major goal of the women’s rights movement - would have barred any unequal treatment under the law for men and women. The other would have mandated presidents be elected by direct popular vote, abolishing the state-by-state Electoral College system that has enabled some presidents, including George W. Bush in 2000 and Donald Trump in 2016, to win the White House despite losing the national popular vote.

With Republican Bob Dole, Bayh also was the force behind a 1980 law called the Bayh-Dole Act that allows colleges and small businesses to gain ownership of federally funded copyrights.

Bayh had hoped to win the Democratic nomination to challenge Nixon in 1972, but set his aspirations aside because his wife, Marvella, was fighting breast cancer. She died of cancer in 1979.

He ran for the 1976 Democratic nomination but lost to Georgia Governor Jimmy Carter, who went on to defeat Republican President Gerald Ford, who had replaced Nixon.

Bayh was angry after losing to Quayle in the 1980 Senate election in which he was targeted for defeat by what he called “right-wing hate groups,” including newly ascendant Christian conservatives.

He said at the time, “I don’t intend to sit still and let it happen in the tradition of Nazi Germany where no one spoke out when it started. It is important to put those haters in their place and let the American people know what is happening.”

Birch Bayh Jr. was born Jan. 22, 1928, in Terre Haute, Indiana. He served in the Army after World War Two in Germany as a military policeman. He returned to college in Indiana and became an amateur boxer. His political career started at age 26 with his election to the Indiana House of Representatives in 1954.

He ran for the U.S. Senate in 1962, with Democratic President John Kennedy traveling to Indiana to campaign for him.

His son, Evan Bayh, served two terms as governor of Indiana (1989 to 1996) and two terms in the U.S. Senate (1999 to 2011).

(This story corrects year of Trump’s election to 2016 in 16th paragraph)