In 1972, he was elected as a Republican to the Ninety-third Congress, defeating future US Senator and Presidential candidate John Kerry, who had moved to the Fifth District to seek the seat after Rep. Morse resigned to take a post at the United Nations. Cronin's victory was a huge upset against the anti-war candidate Kerry. He had trailed at one point by more than 20%, and his victory was often accredited to harsh attacks by The Lowell Sun, which attacked Kerry for being an elitist carpetbagger and for his questioning of the patriotism of those who supported the war.
In the House, Cronin served on the Interior Committee, and began a process that led ultimately to the creation, years later, of an urban park in Lowell. A businessman and non-ideologue at heart, Cronin placed himself in the moderate wing of his party.
In 1974, his first bid for re-election, Cronin faced an assertive challenge from a Lowell-based county commissioner Paul Tsongas, who seized on President Nixon's impeachment troubles in what turned out to be a bad year, electorally, for Republicans nationwide. Tsongas demanded that Cronin release his income tax returns, but the congressman declined;[2] Cronin also declined to debate Tsongas. Tsongas also made political hay over the failure of a technology firm, Mostek, to locate a facility in Lowell after Cronin had promised the firm would do so. A memorable Tsongas radio ad featured echoing footsteps in an empty building. In the November election, Tsongas won 61% of the vote—and went on to become a US Senator and a candidate for President of the United States in 1992.
Cronin later in life would serve a number of positions at Massachusetts Port Authority, and he unsuccessfully sought the GOP nomination for governor against William Weld. In 1992, Cronin won the Republican nomination to regain his old seat against a weak incumbent Chester G. Atkins. However, Atkins, who had been caught up in the House check-kiting scandal, would be defeated in the primary by an up-and-coming Democratic star, Martin T. Meehan, who in turn would defeat Cronin in the General Election 52% to 38%. Cronin died on April 5, 1997, from a brain tumor at Massachusetts General Hospital in Boston, Massachusetts, and was buried in Spring Grove Cemetery in Andover.
