Larison argues that Gary Johnson doesn't have a real shot at the nomination:
...all of the reasons why I would want to support him (e.g., his views on civil liberties, foreign policy, the drug war, etc.) are the reasons why he would be persona non grata for much of the GOP.
Still, his run could do some good:
Like Ron Paul’s run in 2008, a Johnson campaign would be refreshingly oriented toward ideas and policy, and it would show many of the leading candidates to be hypocrites and frauds when it comes to protecting constitutional liberties, balancing budgets, and reducing spending. More than that, it would offer libertarians and traditional conservatives a decent alternative, and it might force some healthy and much-needed debates on the security/warfare state, foreign policy, and the drug war.