Happy thoughts: Is McCain seriously thinking about either hopping the aisle, and/or becoming part of the first split ticket since the Twelfth Amendment was ratified in 1804?
Slightly alarming thought: We are in danger of becoming a one-party nation, in one of two ways. The obvious way is if the Republicans really do manage to establish a long-term majority in both houses of Congress, and a lock on the presidency. The attitude of the Republican leadership towards the truth is, at this point, almost as casual as that of the Soviet Communist party back in the day. Fox News is the inheritor of Pravda. However, there's a more insidious way it could happen. The Republican leadership drives out enough of its moderates that the Republican party collapses for the better part of a decade, and we have one-party Democratic rule for that period -- much like in the 30s. While I largely agree with the current Democratic platform, that would be a very dangerous situation -- like any large, powerful organization, there are plenty of unscrupulous people involved, and the one thing the Rs and Ds have agreed on over the last few decades is that the parties themselves should accumulate as much power over the process of gov't as possible. All it'd take for the Democratic party to turn authoritarian is one or two election cycles with no serious challenge, and a Putin-like charismatic candidate.
No, I'm not really paranoid enough to consider this a likely scenario. But it makes a good set-up for a novel...