If Edwards dropped out, where would his supporters go?

There is a lot of uncertainty about the impact of John Edwards' presence in the race. We often hear the argument that if it weren't for Edwards, Obama or Clinton would be doing better. Yesterday, Matt Stoller discussed Edwards' role in the race for the Democratic presidential nomination as a second tier candidate.

So who would win the Edwards supporters if he dropped out? We can't say for sure, because we don't know who among his supporters will opt to not vote instead of choosing another candidate. Still, there are a couple pieces of information that shed light on this situation.

In addition to asking candidate preference, the New Hampshire exit poll asked the survey respondents about their "Opinion of Barack Obama" and their "Opinion of Hillary Clinton." Doing some spreadsheet math, we can look at Obama and Clinton favorability among Edwards voters:

On the whole, NH residents who voted for Edwards appear to like Obama more than Clinton. Still, there are plenty of people in the "mushy middle" for both candidates. I'd guess that Edwards voters are predisposed toward Obama, but the majority of them are still up for grabs.

Although I haven't seen any numbers, news organizations with access to the Iowa NEP data suggest that Edwards voters in Iowa preferred Obama as a second choice.

Indeed, Edwards voters in Iowa favored Obama over Clinton as their second choice by a nearly two-to-one margin in caucus-night surveys.

Of course, these are just two small states, and not representative of national sentiment. The most recent national survey that I could find with a dataset in the public domain asking the "second choice" question is the Pew April 2007 Political Survey.

So back in April, a third of Edwards supporters favored Clinton as a second choice, and a third of Edwards supporters favored Obama as a second choice. However, the dynamic of the race has clearly changed since then.