In 1972 he was elected in an upset as a Democratic state senator for Iberia and St. Martin parishes. The defunct Baton Rouge State Times named him the "Outstanding Newcomer" of the year after his first legislative session.
In 1975, he was elected, again as a Democrat, as secretary of state in another upset. An opening appeared when Secretary of State Wade O. Martin, Jr., who was then a Democrat but later switched to the Republican Party, stepped down to launch an unsuccessful gubernatorial attempt. Hardy came from behind to beat his fellow Democratic opponent, State Representative P.J. Mills of Shreveport. In the primary, Mills had led with 49 percent of the vote. Hardy prevailed in the runoff -- officially the general election in Louisiana. He polled 388,780 votes (51.5 percent) to Mills' 366,510 (48.5 percent).
Because he is fluent in French, Hardy was invited to represent the United States in an international government seminar in Quebec, Canada, in 1976.
In 1979 Hardy ran for governor. Endorsed by former Governor John McKeithen, he carried 18 parishes in the jungle primary, but he missed securing a general election berth by 4 percentage points. Hardy finished in fourth place with 227,026 votes (16.6 percent). In a disputed third place was outgoing Lieutenant Governor James E. "Jimmy" Fitzmorris, Jr., of New Orleans, with 280,760 (20.6 percent). The general election would feature Republican David C. Treen of Jefferson Parish, with 297,674 (21.8 percent), and Public Service Commissioner Louis J. Lambert of Ascension Parish, with 283,277 (20.7 percent). Hardy hence lost a general election slot by some 56,000 votes. Though he was still a Democrat, Hardy endorsed Treen. Thereafter, Treen, who narrowly defeated Lambert in the general election, appointed Hardy as Louisiana’s secretary of transportation. While there, he supervised the spending of a record $2 billion on highways. When Hardy resigned the transportation post, Treen elevated the assistant secretary, Tom Colten, to the top position. Colten's tenure was one of the longest in the position: he served until his retirement in 1993.
When Hardy vacated the secretary of state's position, the two top votegetters, Sandra Thompson, director of the Atchafalaya Basin Culture, Recreation, and Tourism project, and State Senator James H. "Jim" Brown of Ferriday, went into a general election showdown. Brown emerged a narrow winner.
Hardy switched parties and ran for lieutenant governor as a Republican in 1987. Six candidates sought the position, including the two-term Democratic incumbent Robert Louis "Bobby" Freeman of Plaquemine in Iberville Parish. Also in the race with Freeman and Hardy was Democrat William Ford "Bill" Dodd of Baton Rouge, son of former Democratic Lieutenant Governor William J. "Bill" Dodd, who served from 1948-1952. Primary results gave Freeman 586,335 (40 percent), Hardy 429,906 (29 percent), and Dodd 242,519 (17 percent). Three other Democrats polled a total of 14 percent of the primary vote.
In the general election held on November 21, 1987, Hardy upset Freeman, 521,992 (53 percent) to 460,199 (47 percent). While Hardy was winning as lieutenant governor, State Representative W. Fox McKeithen, son of John McKeithen, was elected to Hardy's former position as secretary of state. Incumbent Secretary of State James H. "Jim" Brown, originally from Ferriday in Concordia Parish, who had succeeded Hardy in 1980, had vacated the post to make an ill-fated run for governor.
As lieutenant governor, Hardy led the way to enact legislation creating "Tax Free Shopping," which still today gives foreigners an incentive to visit Louisiana. In turn, this concept has resulted in tremendous increases in tourism-related jobs, and in 1989 alone increased tourist spending by a record $1.2 billion.
In 1985, Hardy had assisted local entrepreneurs in the production of the full length feature film of the Cajun movie Belizaire the Cajun which was filmed in at Acadian Village in Lafayette. He was the associate producer and played a bit part in the movie. Under his leadership thereafter as lieutenant governor, the economic impact of the movie industry increased by $51 million.
In 1989, Phi Kappa Theta national fraternal organization presented Hardy with the "Man of Achievement” award. In 1991, he was presented the New Orleans World Trade Center’s highest award, “The Order of the Plimsoll”.
Hardy was defeated for reelection as lieutenant governor in 1991 by the Democrat Melinda Schwegmann of New Orleans, daughter-in-law of Jefferson Parish state legislator, gubernatorial candidate in 1971, and grocery mogul John G. Schwegmann, Jr., (1911-1995). In the jungle primary, Hardy and Schwegmann virtually tied, 624,371 (43 percent) for Schwegmann and 620,199 (also 43 percent) for Hardy.
In the general election, Schwegmann scored a large victory, 1,009,026 (59 percent) to Hardy's 693,412 (41 percent). There was speculation that Schwegmann benefited from coattails of Democratic gubernatorial nominee Edwin Washington Edwards, who won his fourth nonconsecutive term as governor in that same election over the controversial Republican David Duke. Edwards polled 1,057,031 votes (61 percent) to Duke's 671,009 (39 percent). Hardy hence ran just some 22,000 votes above Duke's tabulation. Hardy thereafter retired from politics.
After she left the office of lieutenant governor, Schwegmann switched to the Republican Party. After a stint in the legislature, she attempted to regain the lieutenant governorship in the 2003 jungle primary but was badly defeated by Democrat Mitch Landrieu, brother of U.S. Senator Mary Landrieu.
Hardy is an attorney, banker, businessman, and political consultant residing in Baton Rouge with his wife Sandra Gatlin "Sandi" Hardy (born 1943), a native of Grant Parish in north Louisiana. They have two children and two granddaughters. Gregory Paul Hardy (born 1966) is an attorney in St. Martinville, and Yvette Hardy Gross is a University of Louisiana at Lafayette graduate living in Baton Rouge.