Donald Trump wasn't invited to address some 450 top conservative donors who gathered here at a lush oceanfront hotel for a policy-focused retreat hosted by the Koch brothers and their powerful political network.

So the real estate magnate turned to Twitter on Sunday to mock rivals -- former Florida Gov. Jeb Bush, Florida Sen. Marco Rubio, Wisconsin Gov. Scott Walker, Texas Sen. Ted Cruz and former Hewlett Packard chief executive Carly Fiorina -- who were given entrée to potential backers at the luxurious gathering.

"I wish good luck to all of the Republican candidates that traveled to California to beg for money etc. from the Koch Brothers," Trump tweeted Sunday. "Puppets?"