No, Trump is the ONLY electable candidate despite bogus polls showing Carson winning. Moreover, traditionally the primary winner coalesces either all or most of the GOP support. Even Romney got most--it's a myth that 4 million GOP voters stayed home (Romney exceeded McCain's 2008 vote, especially in key states).
That is a much mis-understood point. And since Romney exceeded McCain's votes, the real reason he lost is because the democrat voters were more energized for Obama. The 47% comment by Romney scared the heck out of democrats. If my personal democrat contacts are any indication, the only republican they will consider switching party loyalty is for Trump. Ted Cruz will bring democrats out of the wood work to vote for Hillary.