For all the hand-wringing over an extended primary campaign, including some hand-wringing of my own, all quantitative evidence currently points to the campaign benefiting the party. The extended primary campaign is creating vast numbers of new Democrats, improving our general election standing, creating new swing states, turning existing swing states blue, allowing small donors to take over direct funding the Democratic Party in the Presidential election, and swamping Republicans in fundraising. First, Rasmussen finds a 7% shift to Democrats in partisan self-identificaiton:
In February, the number of Americans who consider themselves to be Democrats jumped to 41.5%, the highest total on record. Just 31.8% consider themselves to be Republicans. The partisan gap-a 9.7 percentage point advantage for the Democrats-is by far the largest it has ever been. The previous high was a 6.9 point edge for the Democrats in December 2006. Rasmussen Reports tracks this information based upon telephone interviews with approximately 15,000 adults per month and has been doing so since November 2002.
The 9.7 percentage point advantage for Democrats is up from a 5.6 point advantage a month ago and a 2.1 point advantage two months ago. The surge for the Democrats is especially notable because it reversed a modest trend in the GOP direction that unfolded over much of calendar year 2007.
AP confirming Rasmussen:
More people say they are Democrats than said so before voting started in this year's presidential contests while the number of Republicans has remained flat, a survey showed Thursday.
The Associated Press-Ipsos poll had additional bad news for the GOP: The number of independents and moderates satisfied with President Bush and the country's direction has dipped to record or near-record lows.
That is a seismic partisan shift of about ten million Americans that would not have happened without the epic nomination campaign. Also, according to Real Clear Politics, both Clinton (+0.5%) and Obama (+5.6%) have now taken the lead against McCain in general election polling, even though in January they both trailed. Further, compared to McCain's $12M February haul, Clinton and Obama combined to raise between $86M-$90M in February, $75M of which came from small, online donors. Yet further, extensive campaigning in states like Texas and making them surprising competitive in the general election, while heavy campaigning in states like Ohio are making them virtually solid blue states for the general election (see here for more).
Overall, the extended nomination campaign has been excellent for the Democratic Party. A big test of just how good things are, and also of Obama's ability to carry his wave downticket, will come on Saturday during the special election in IL-14 for Dennis Hastert's old seat. There are still nightemere scenarios, too. First, Obama could use his large delegate lead to eek out the nomination even if he loses the majority of the remaining primaries, and having a nominee who stumbles to victory will be terrible in terms of general election momentum. Second, Clinton could win the nomination through superdelegates, arm-twisting and the credentials committee despite losing the popular vote, which could cause a huge number of disaffected Democrats in the general election. However, if the nomination is decided pretty much any other way, even if it doesn't end until June the extended nomination campaign will have been a great overall boost to Democrats. Small donors are taking over, massive organizing is taking place in long-ignored states, candidates are forced to continually improve after stumbling, waves of new Democrats are being created, McCain is getting shut of the media and swamped in fundraising.
This could change, but so far the extended nomination campaign has been a huge boost to the Democratic cause, and longstanding worries about the negatives of hotly contested primaries are proving both false and very old-fashioned. When the entire country is transfixed on Democrats, when Democrats are forced to compete everywhere, and when large donors are out of money, amazing things can happen. It appears that creating nationwide excitement is a more effective way of building up the party rather than falling sheepishly in line after New Hampshire.
Update: Brendan Nyhan has specific data that shows divisive primaries do not harm candidates in the general election.