A detailed national poll (Los Angeles Times/Bloomberg) in late June 2008 shows that, as a candidate for President, Ralph Nader pulls 3 times more votes from McCain than from Obama. This is the opposite of the conventional wisdom.

When Nader and Bob Barr are added to the race, Nader pulls away 6% of McCain's support but only 2% of Obama's support. Barr pulls away 5% of McCain's support and 0% of Obama's support. So having both Nader and Barr in the race reduces McCain's vote by 11% and reduces Obama's vote by only 2%.

Thus, it appears that the Democrats should be encouraging both Nader and Barr to qualify for state ballots.

The full study is at http://www.calendarlive.com/media/acrobat/2008-06/40351172.pdf