U.S. Sen. Lincoln Chafee's tough fight to overcome conservative challenger Stephen Laffey in Tuesday's primary in Rhode Island, and the stunning defeat of three-term incumbent Democratic Sen. Joseph I. Lieberman in the Connecticut primary, are among the final steps in a process that began more than 40 years ago in San Francisco at the Republican National Convention.
There, conservatives finally prevailed and nominated one of their own, Sen. Barry Goldwater of Arizona, as their standard bearer. With the nomination in hand, Mr. Goldwater then did a rather remarkable thing, an act that would eventually result in the tipping of power in both parties - and in so doing, would create the modern Republican and Democratic parties.
Until Mr. Goldwater's 1964 run, when a nominee of one ideology was chosen for president in either party, he would pick a running mate from the other side of the ideological spectrum. Thus, when the liberal Franklin D. Roosevelt was chosen in 1932, he picked the more conservative John Nance Garner of Texas for vice president. In 1952, liberal Republican Dwight Eisenhower chose the conservative senator from California, Richard M. Nixon, as his running mate.
This "ticket balancing" to the pragmatists in both parties - "ticket splitting" to the purists - was designed to produce unified conventions, which tended to win the fall elections. In 1964, 1976 and 1992, the GOP was divided at its conventions. Republicans lost each of those elections. In 1968, 1972 and 1980, the Democrats were divided and also went on to lose. In 1960 and 2000, both parties were united at their national conventions and - lo and behold - those years saw two of the closest elections in American history.
But Mr. Goldwater changed history by choosing the equally conservative congressman from New York, William Miller, as his running mate. Mr. Miller was then chairman of the Republican National Committee and was unremarkable except that he had a knack for getting under President Johnson's skin.
When the curmudgeonly Arizonan failed to pick a moderate, as many had expected him to do, moderates and liberals in the GOP were appalled. Republicans of that stripe left the party in droves, and Mr. Goldwater was clobbered in the fall election.
But in choosing Mr. Miller, Mr. Goldwater also began the process of attracting conservative Democrats into the GOP, upsetting the delicate equilibrium both parties had operated under for years. Thus, in later years, the conservative Democratic governor of Texas, John Connally, became a Republican, while the liberal Republican mayor of New York, John Lindsay, became a Democrat. The former head of Democrats for Nixon, Ronald Reagan, changed his party registration to Republican in late 1964.
The process was furthered in 1972, when the Democrats nominated possibly their most liberal standard-bearer ever, Sen. George McGovern, a prairie populist from South Dakota. At the convention, Mr. McGovern chose Thomas Eagleton of Missouri, someone nearly as left-wing as Mr. McGovern himself. Mr. Eagleton was forced from the ticket when it was revealed that he had undergone electroshock therapy, and he was replaced by the genial Sargent Shriver, a Kennedy consort and thus another liberal. Mr. Nixon and Spiro Agnew smashed the "acid, amnesty and abortion" ticket in the fall.
Licking their wounds, Democrats moved back to the center in 1976 with the nomination of Jimmy Carter, but this was an anomaly brought on by Watergate and a large and inept field of candidates whom Mr. Carter bested.
Ticket splitting still took place thereafter, but the ideologies of running mates moved closer and closer, and the parties would thus become more and more polarized.
The Republican Party, with the demise of the "Wednesday Club," a group of liberal GOP senators, would become solidly right of center. The Democrats, led by Bill Clinton and the Democratic Leadership Conference, would attempt - and succeed for a time - to make their party more centrist. Mr. Clinton accomplished this through the force of his personality, but once he left the scene and his vice president, Al Gore, was nominated in 2000, the last hope of keeping the Democrats less than ultraliberal collapsed.
Now, iconoclasts such as Zell Miller and Christine Todd Whitman are exotic, if not endangered, species within their own parties and the DLC is irrelevant. It is no wonder Senator Chafee, the Senate's most liberal Republican, faced such a strong challenge from his conservative primary opponent.
Given this climate of political polarization, and with Democrats threatening to recapture both chambers of Congress, Republicans, now more than ever, need to appeal to the party's base. Only by appealing to the populist, conservative base can Republicans hope to get their people to the polls and avert a disaster in November.
Craig Shirley, president of Shirley & Banister Public Affairs, is the author of "Reagan's Revolution: The Untold Story of the Campaign That Started it All," about the 1976 campaign. His e-mail is email@example.com.