E .J. Dionne argues that they are.
We will have evidence soon enough, but it is commonly argued that highly motivated, ideologically driven party members, even if they are a minority, can pull either of the major political parties far enough to either ideological extreme that they become uncompetitive in the long run. It happened to Democrats in the 1960s, 70s and 80s and it could, possibly, be happening now to Republicans.
One culprit may be the primary election process which -- through the miracle of low voter turnout -- allows a small, focused group of people to select a party's candidates and issues. These candidates and issues might be competitive for an election cycle or two, but overtime they might turn the party off to the moderate middle (the one's who tend not to get worked up over politics and are often likely to vote only in presidential elections).
That's the theory anyway. It looks like it might get tested in the next couple of years. Of course this only matters if the aggregate opinions of the general public are fixed. If public opinion moves to the right, this doesn't matter. But considering how volatile the electorate has been over the past few years, it is not unreasonable to suspect that a motivated and highly conservative voting bloc might control Congress after this election, but will set an agenda that will lead to a moderate to liberal counter mobilization in 2012. That's basically what happened after 1994. So will Obama 2012 be a replay of Clinton 1996? That's my prediction.
