Primary elections always matter. But some primary elections matter more than others; indeed, some primary elections define the character not just of a particular official’s term, or even of a legislative or congressional session, but of the nation’s politics for years to come.

Residents of the state of Wisconsin, where my family has resided for seven generations, know this better than the citizens of most states. Sixty years ago this month, Republican primary voters turned out one of the greatest senators in the history of the United States, Robert M. La Follette Jr., and replaced him with one of the lousiest excuses for an elected leader this country has ever produced, Joe McCarthy.

The Wisconsin Republican Senate primary of 1946 set the wheels in motion for the Red Scare of the 1950s, to which McCarthy lent his name and his sordid tactics. It is true that Richard Nixon and others would have ginned up some sort of anti-communist propaganda campaign, but it is doubtful that it would ever have done the damage to civil liberties and public life that McCarthy achieved with his unparalleled lies and cruelty.

That Republican primary also began the long descent of the Grand Old Party, which had once laid a far stronger claim than the Democratic Party to the progressive mantle, into the pit of petty bigotry, reaction and neoconservative fantasy that now defines it.

La Follette lost by only 5,000 votes in August, 1946, but the margin did not matter. With the defeat of the maverick senator, who had supported extension of Roosevelt’s New Deal at home while wisely questioning schemes for post-World War II military adventures abroad, the era of the old-school Midwestern progressivism came to a close. And American politics entered a dramatically uglier and more irrational period from which it has yet to fully emerge.

If anyone doubts this, consider the recent editorial attack on Ned Lamont, the mainstream liberal who defeated U.S. Sen. Joe Lieberman in Connecticut’s Aug. 8 Democratic primary, by the conservative Waterbury Republican-American newspaper.

Entitled “Ned Lamont’s True Colors,” the Sunday editorial in one of Connecticut’s larger daily newspapers was classic McCarthyism. “Red Ned may label himself a progressive, but when he espouses goals shared by Marx, Lenin, Stalin, Castro, et al., he gives away his true color,” wrote the paper’s editors of Lamont, a successful businessman who espouses views no more radical than those of U.S. Sen. Russ Feingold, D-Wis., and dozens of other House and Senate members including a few anti-war Republicans.

The newspaper alleged that “(Lamont) has surrounded himself with people who may be characterized fairly as dedicated socialists and borderline communists,” when in fact Lamont’s primary supporters were grass-roots Democrats who were frustrated with Lieberman’s allegiance to the Bush administration’s failed foreign policy.

The Republican-American editorial also claimed that “liberal journalists adore (Lamont) because they share his world view on abortion, homosexual marriage, universal health care, racial quotas, loopy environmentalism and especially the war against Islamic terrorism. They are blood brothers, or more accurately, fellow travelers. Just as journalism has become a hornet’s nest of socialism (communism not yet perfected), if you shake Lamont’s family tree, a lot of Red apples will fall.”

Spouting innuendo and inaccuracy with abandon, the newspaper sought to claim that Lamont’s blue-blood family including J.P. Morgan’s partner, Thomas Lamont, and civil libertarian Corliss Lamont was nothing less than Stalin’s fifth column in the United States. The paper conveniently forgot to mention that Corliss Lamont, though certainly a man of the left, authored a much-noted tract titled “Why I Am Not a Communist.”

While the Republican-American may be guilty of lax journalism, the real shame belongs to Lieberman’s independent campaign, which has spread the Waterbury paper’s fantastic claims. The senator’s communications director even quoted the editorial in a widely circulated statement on the race.

With the help of the Waterbury Republican-American, Joe Lieberman is keeping alive the politics of another Joe: the one named McCarthy. And in so doing, Lieberman’s proving that the shock waves from a primary election in the summer of 1946 are still being felt in this summer of another primary election that has dislodged another senior senator.