McCarthyism? That sounds fun.
If you ever see an "ism" named after a person, chances are that person is…controversial. And wouldn't you know it? McCarthyism, the lingering legacy of Senator Joe McCarthy, is basically used to describe public blackmail and fear-mongering, done to score cheap political points and suppress dissent.
So who was this guy who's basically the political villain for the entire decade of the 1950s? He started, humbly enough, from a large Irish-American family in a small community near Appleton, Wisconsin. He got his law degree from Marquette University, and could have had an undistinguished career with nary an "ism" to be found.
By 1935, he was already flirting with politics, running for district attorney as a Democrat and losing, before running for circuit judge as a Republican and winning. He was already using shady tactics, lying about both his and his opponent's age in his campaign literature.
When World War II broke out, McCarthy enlisted in the Marines, where he was stationed in the Pacific. Though he'd claim he flew in 32 combat missions, the number was actually 12, and as a gunner-observer. McCarthy was just as dishonest about his own achievements as he was about the alleged crimes of others. He had some pictures taken while in the gunner position on an aircraft; that's where his "Tail Gunner Joe" nickname came from.
Kylo Ren—er, Joe McCarthy—Rises to Power
In 1946, McCarthy got the Republican nomination for one of Wisconsin's Senate seats. In a dirty campaign, he defeated incumbent Robert La Follette, partially by accusing the man of cowardice for not enlisting in the Armed Forces during WWII. That La Follette was too old to enlist never bothered McCarthy.
(P.S. La Follette's later suicide is sometimes blamed on McCarthy.)
McCarthy was relatively undistinguished until the infamous Wheeling Speech when he alleged (read: made up) that he had the names of 205 Communists working in the State Department. This number kept fluctuating as McCarthy workshopped the speech around the country (part of the point of Welch's later needling in the hearing). For a frightened and angry populace, McCarthy was just the ticket to ferreting out these enemies of the country.
McCarthy wasn't universally popular, though. While Nixon and fellow red-baiters loved him, Dwight Eisenhower was not a fan. When Ike was elected (and McCarthy re-elected), he was reluctant to condemn the popular Senator in public even though he said in private that he "despised" the Senator's tactics (source). Instead, McCarthy was placed on the Senate Committee for Operations, where Ike thought he'd stay out of trouble.
McCarthy realized that he was now in charge of the SCO's Permanent Subcommittee on Investigations, and instantly expanded that group's mandate to look for Communists in government. Over the next two years, he violated civil rights left and right and got more than 2000 government employees fired, all while never managing to evidence of Communist infiltration.
By March 1954, McCarthy also ran afoul of distinguished broadcast journalist Edward R. Murrow, host of the popular documentary TV show See it Now. Murrow used McCarthy's own words to show how the senator used empty demagoguery to stir up emotion, and pointed out the hollow nature of McCarthy's arguments and evidence. It was the first time someone stood up to the bully from Wisconsin, and the first sign that public sentiment was beginning to turn.
Fortunately for the world, McCarthy didn't know the word "hubris." Flush with success, he backed Roy Cohn's play to extort the Army on Schine's behalf. McCarthy didn't realize he was challenging the most sacred institution in American politics to a fistfight. The Army said McCarthy was trying to get preferential treatment for Cohn's friend David Schine, and McCarthy leaned on the only accusation he ever had: "Communistscommunistscommunists."
Welch utterly crushed McCarthy by exposing the senator's utter lack of decency. The Senate condemned him, and though this was little more than a slap on the wrist, it was the end of his influence. His health tanked, too. He drank.
Though Communist infiltration continued to be an obsessive national concern, McCarthy was a shadow of himself. He never got mentored by someone looking for a redemption angle. He never got an inspirational montage. Though he didn't die until 1957 (of cirrhosis of the liver, likely brought on by alcoholism), his political career was over as soon as Welch slapped him with the decency line.
McCarthy faded into legend, "-ism" and all.