Just put him on the GOP ticket in 2008:

Is it too fanciful to speculate about a 2008 GOP ticket of McCain-Lieberman, or Giuliani-Lieberman, or Romney-Lieberman, or Allen-Lieberman, or Gingrich-Lieberman? Perhaps. But a reinvigorated governing and war-fighting Republican party is surely an achievable goal. And a necessary one.

Yea, dig that great, war-fighting party.