I think it is possible. Orthodoxy continues to be on the rise in America, and protestantism on the decline. The traditional WASP churches stand for little, if anything, anymore, evangelical protestantism the exception.
There are currently 2 Orthodox senators (Olympia Snowe of Maine and Sarbanes of Maryland), but they are more nominal than anything, as was Michael Dukakis. You can't see their faith reflected in their votes.
I think an Orthodox candidate would do well if he voted his convictions, going along with his faith, rather than telling the public what he thinks they want to hear. Americans respect that. It's hard to tell that the current Orthodox politicians are Orthodox at all.
We may not see it in our lifetime, but I think it is possible.