I think Trump's the back-up plan. Ron Paul is the first option. When he announced his retirement from the House, I'm pretty sure he was telegraphing a third-party run. Judging by the fawning coverage and overt fundraising for Paul on Russia Today TV, he appears to have the full support of the Kremlin in disrupting this election and delivering a second Obama term.
What’s interesting is that Palin has somewhat courted both of those guys. Standing strong for Trump when others were mocking him and endorsing Ron’s son Rand when he was an underdog.
Don’t know or expect that any of that would have any power over them—note Bachmann and Perry—but it’s still interesting.