US political parties - ignoring the centre

Recent news that the Tea Party movement has made definite in-roads into the mainstream Republican party with the selection of Rand Paul as the Republican candidate for the Kentucky Senate seat.
Very good analysis of Dr Paul's policies here and an interesting piece about the implications of the Tea Party movement here by the "Democracy in America" blogger in the Economist.

For G&P students this is all useful stuff because it emphasises how political parties are increasingly relying on very vocal groups and excluding the large number of "independent" and moderate voters. The Tea Party movement may have won the primary, but this does not necessarily translate into a win for the Republican party:

Last year's New York state by-election comes to mind. A conservative populist ousted a moderate Republican, and subsequently lost the Republican seat to a Democrat... All this said, it remains likely that the Democrats will take a whacking in November. But an organised and disciplined Republican Party offering a viable set of alternative policies—think 1994's "Contract With America"—would whack them a lot harder. Instead, populist anger has enraged people against Democrats, with few tangible benefits to Republicans so far.

The Tea-party does not have an organisational centre or a clear set of policies, all of which encourage a wide-range of anti-government types to support it, but does not lead to success against a clear set of policies which could be supported by a significant number of independent voters.

There is a very interesting (if very long) analysis of the state of the parties in the New York Review of Books. A couple of things struck me:

The ideological polarization between Republicans and Democrats that surveys pick up is owing almost entirely to the radicalization of those belonging to the shrunken Republican base. (As of 2009, only a quarter of Americans identified themselves as Republicans, the lowest figure since the post-Watergate years.)

Democrats have edged slightly more left on political and economic issues, whereas the views of independents, the largest and fastest-growing group of voters, have not changed much over the years. While well over half of Republicans say that they would like their party to move further to the right, just as many independents wish it was less conservative or would stay where it is.

All of which is useful for any question asking about the importance of political parties in the US - the decline / renewal argument which we can add into the established information.