Unlikely but pretty freaking crazy. As this article points out:
McCain's proposal to kick Russia out of G-8 is bold and unlikely
John McCain dropped a little-noticed bombshell into his March foreign-policy address: Boot Russia from the G-8, the elite club of leading industrial democracies whose leaders try to coordinate economic policies.
One major problem: He can't do it because the other G-7 nations won't let him.
But the fact that he's proposing to try, risking a return to Cold War tensions with the world's second-largest nuclear power after 20 years of prickly partnership, raises questions about McCain's judgment. It also underscores that many of his top foreign-policy advisers are of the same neo-conservative school that promoted the war in Iraq , argue for a tougher stance toward Iran and are skeptical of negotiating with North Korea over its nuclear program.
How do we get to the point where someone running for president is suggesting a basic return to the cold war, but the only thing we care about is some silly thing Hillary said or what crazy thing Obama's former pastor did today? Policies, people: policies. Let's keep this one in the news.
A senior U.S. official who deals with Russia policy said that even Moscow would have to approve of its own ouster, given how the G-8 works.
"It's not even a theoretical discussion. It's an impossible discussion," said the senior official, who requested anonymity because he wasn't authorized to speak publicly. "It's just a dumb thing."
Come on now. First simply ridiculous economics, and now ridiculous foreign policy? We should be wiping the floor with him, not focusing on some dumb thing Clinton said.
Aside from that, many wonder whether McCain's suggestion would be wise policy. They fear that if McCain is elected and follows through on an attempt to toss Russia from the group, it could anger and isolate Russia , which has been increasingly assertive on the world stage, autocratic within its borders and is the second-largest producer of the hydrocarbons that feed the world's energy needs.
...
The proposal also seemed at odds with the theme of McCain's speech, which promised a less unilateral approach to world affairs than the Bush White House has pursued.