So, it looks like Nader might have cost Obama the state of Missouri. Check it out:
- McCain: 1,445,812
- Obama: 1,442,810
- Nader: 17,813
- Barr: 11,386
If you assume that 3rd party voters would have voted for their more closely aligned major party candidate, had their 3rd party candidate not been running, Obama would've seen an upswing of 6500 votes in his tally, which is twice as many votes as he would've needed to take the state.
Fortunately, Nader ended up being completely irrelevant in this Presidential cycle.