It happened in Russia after the communist revolution. The communists seized power, overthrowing the Czars. But the party was too big, unwieldy. Too many people had their own opinions and party dissent was evident.
Under Lenin, the first purges were expulsions, not arrests and executions. Those expelled were intellectuals in various disciplines, people who were intelligent, could persuade others, and were not content to be told what to think or how to act. They were not unsympathetic to the Revolution, though. In fact, they agreed with it for the most part. They may have favored other methodologies or different directions going forward.
But in any case, their voices were not welcome by Lenin and other party leaders. They would not participate in the hysteria needed to support the party through hard times.
Stalin, Lenin's successor, continued to carry out party purges under various guises, usually having those purged executed along with their families.
Hitler similarly purged the Nazi party of dissent and challengers, executing those who disagreed with him or sought to challenge his power. The Nazi party was built along rigid lines of control, so that dissent from within would be squashed immediately.
A modern-day analog of the same thing can be seen in Afghanistan. The Taliban, a small group in numbers but fiercely devoted to their ideology, kills villagers who cooperate with the US, attacks schools for girls, and generally controls the population with a reign of terror.
Granted, the purge happening in the Republican Party is not as dramatic, not as bloody, but it is just as decisive in its ideological isolation. The party began emphasizing lack of cooperation with Obama and the Democrats right after Obama's election in 2008. Since Obama took office, the constant mantra of the Republicans has been "obstruction." The rhetoric against the administration, against the Democratic members of Congress, and against Obama personally was marked by hate, vitriol, and outright lies -- often colored with racism. The point has always been to de-legitimize the President and his administration.
And threats have been made against Republicans who would dare to cooperate. Several Republicans , characterized as RINOs - Republicans in Name Only -- have lost their primaries, having incurred the wrath of Tea Party purists who believe in no cooperation with a black president and a democratic congress.
The Republican Purge, begun when Obama became President, has intensified. It will continue. The party is moving toward an ideologically "pure" position -- no taxes, no government, no regulation of business, no health care, no protection of the poor and the destitute, no Social Security or Medicare, survival of the richest, no rights of birth control or abortion, an enhanced police state, allowing racism and discrimination, intolerance of Islam and homosexuality, and a perpetual state of war. All of this in the name of Christianity, mind you. Many of the positions taken are ostensibly "Christian" positions -- the fundamentalist variety. More moderate or liberal Christians would see concern for the poor and social justice as Christian virtues.
Now not all Tea Party Republicans hold to all these radical positions. But you can bet that unless a wave of sanity comes over the party, there will be more purges. We have already seen accusations of "tea party in name only" as candidates try to outconservative the other.
Remember, the purge began when Obama got elected. One by one even mainstream Republicans have adopted more radical language and attitudes in an attempt to survive politically.
Although the Democrats technically have had control of the Congress and the White House, control does not mean the ability to get things done. Senate rules require a super-majority of 60 votes to move a bill to a voting position, and the Democrats do not have that. Nor do Democrats act in lockstep. The Democratic values of diversity and differences of opinion mean that they are less united against a lockstep minority -- and the Republicans in adopting that kind of attitude have won the day time and again. They scream for the Administration to treat them fairly, to include their ideas, to compromise -- and then vote against whole measures. Health care was significantly weakened because the Administration wanted to treat them as reasonable and rational when they were determined to be unreasonable, irrational, and obstructionist.
The public values getting things done. A diverse majority will wind up at the mercy of a united minority moving with a single purpose. It happened in Russia. It happened in Germany. It may well happen here, if we don't learn the lessons of history. George W. Bush presided over the greatest deconstruction of government that has ever occurred, while increasing its police powers and warmongering. The Tea Party Republicans will make Bush look like a big government regulator.
Rand Paul wants to deregulate the coal industry after the terrible Massey coal mine accident. Who needs safety regulations? He also wants the ability for individuals and businesses to discriminate against blacks. Sharron Angle has called for the elimination of Social Security, Medicare, and unemployment insurance.
Think they can't do it? Look what chaos crazy minorities produced in Russia and Germany. But this is America! Yes, but the Tea Party folk do not like a tolerant America where people do what they please and government is there to help people in trouble. They object to things like the 14th Amendment which outlawed slavery and gives citizenship to people born in the US. Some object to the people being allowed to vote for their Senators! Some have even objected to the amendment giving women the vote.
A reasonable majority is usually helpless at the onslaught of a determined, single-minded minority. And if the Republican Tea Party seizes control of Congress, the dismantling of America will begin.