Some on the left attack them as fascists or racists, though evidence of that is sorely lacking. David Brooks in The New York Times compared them to the New Left campus radicals of the 1970s, which comes closer to reality but doesn't quite ring true.
Some tea partiers, citing the Declaration and the Constitution, compare themselves to the patriots of 1776 and the founders of 1787, which has some validity but seems overly self-congratulatory.
In terms of their immediate effect on conventional politics and their potential for continued influence, I think the tea partiers bear an uncanny resemblance to the antiwar activists in the Vietnam War period.
Like the tea partiers, the antiwar folk did not start off affiliated with one political party. They campaigned against an incumbent Democratic president and his political heir in 1968. Four years later, some supported Rep. Pete McCloskey's antiwar primary challenge to Richard Nixon. The tea partiers have plenty of corrosive things to say about the Republican politicians of the last decade, and at least some of them may support likeminded Democrats.
But if they stay involved, the tea partiers are likely to gravitate to the Republican Party, just as the antiwar folk gravitated to the Democratic Party, on which they had a long-lasting and pervasive effect.
Not all of that effect was positive. Antiwar Democrats beat hawks in primaries and then lost general elections to Republicans. The disarray of the 1968 Democratic national convention helped beat Hubert Humphrey, and the antiwar 1972 nominee George McGovern lost 49 states. Some antiwar folks voiced an anti-Americanism that turned off ordinary voters.
But antiwar Democrats supplied energy and impressive recruits to their party. Many Democrats who were motivated by dovish views and supported by dovish volunteers and contributors won breakthrough victories in 1974, enabling the party to hold congressional and legislative majorities for much of the next 20 years. And even as Democrats lost support from white Southerners and blue-collar men, their antiwar tendency helped them win support from affluent and culturally liberal suburbanites who now, despite Democrats' workingman rhetoric, form the dominant part of the party base.