Should've linked this last week, but had a good class discussion on the matter today.  I'll let EJ Dionne take care of the summary:

 Is there room in the Republican Party for genuine moderates? Truth to tell, the GOP can't decide. More precisely, it's deeply divided over whether it should allow any divisions in the party at all.

That's why the brawl in a single congressional district in far Upstate New York is drawing the eyes of the nation. Conservatives are determined to use the race to prove that there is no place in the party for heretics, dissidents or independents. 

When local Republicans picked a moderate, Assemblywoman Dede Scozzafava, as their candidate for the Nov. 3 contest, many on the right rebelled. They are backing a third-party conservative, Doug Hoffman, and he may well drive Scozzafava into third place. For the moment, at least, polls show that Bill Owens, the Democratic candidate, has jumped into first place on the split.

 It demonstrates just how right-wing some Republicans have become that former House speaker Newt Gingrich is on the moderate side of this civil war against his old nemesis Dick Armey, who served under Gingrich as majority leader.

Gingrich, who backs Scozzafava, always understood that he would never have become speaker without help from Republican moderates. Armey prefers ideological purity and, like fellow members of the Tea Party movement, is supporting Hoffman.

The GOP's battle of Plattsburgh and Oswego underscores the fact that while the Democrats are a coalition party uniting moderates and liberals, Republicans threaten to become a party of the right, and only of the right. That means (as we are seeing on health care) that many of the big arguments take place almost entirely inside the Democratic Party.

Not much of a "threat" about it.  The Republicans are pretty much there as a party of the right and only of the right.  This is most definitely not the path to a returned majority, but to permanent minority status.  Back to EJ:

Democrats won their majority in Congress by uniting and firing up their base (George W. Bush helped a lot) and by winning over moderates and independents, often by running moderate candidates in conservative districts. These candidates were typically to the left of the Republicans on economic issues but to the right of, say, Berkeley and Cambridge.

In the meantime, middle-of-the-road voters who had populated the moderate Republican heartland, notably in suburban areas of the Northeast and Midwest, shifted steadily Democratic, turned off by the increasing dominance of Southern conservatives in the party of Lincoln.

Such voters threw solid Republican moderates out of office -- among them Connie Morella in Maryland, Jim Leach in Iowa and Chris Shays in Connecticut -- not because they disliked these champions of the middle way but because all three came to be seen as enablers of a right-wing congressional majority.

The political parties scholar in me is fascinated by the Republican party's rush off an ideological cliff.  Ideological purity simply does not make for majorities in a two-party system.  The Democrat in me says, keep on going.