Three potential Republican presidential candidates appeared before wealthy conservative political donors brought together by billionaires Charles and David Koch in California on Sunday night.

Newsweek reports the Koch event spanned two days. Eight possible Republican candidates made speeches at an assembly in Iowa on Saturday.

On Sunday, another gathering was held at a luxury resort near Palm Springs that drew Republican Senators Marco Rubio from Florida, Rand Paul from Kentucky and Ted Cruz from Texas, and at least 450 supporters and donors.

The Koch brothers, successful industrialists who subsidize conservative causes across the nation, organized the event to give Republican presidential hopefuls access to their private network that has spent hundreds of millions of dollars in recent elections.

Wealthy donors attended in hopes to find a Republican nominee that can win the 2016 presidential election.

At least a dozen Republicans are interested in the 2016 presidency, including former Florida governor Jeb Bush, former Republican presidential nominee Mitt Romney and Republican New Jersey governor Chris Christie. Christie has created a political action committee to raise money for a potential 2016 presidential bid, the Wall Street Journal reported Sunday.

On Sunday night, the Freedom Partners Chamber of Commerce, a non-profit organization supported by the Koch brothers, hosted Rubio, Paul and Cruz to discuss domestic and foreign policy. The senators' discussion focused on abolishing poverty and whether or not a federal minimum wage was a viable solution.

"I think the minimum wage constantly hurts the most vulnerable," Cruz said.

Rubio is sending clear signs about an expected run for the 2016 presidency. He is working hard to keep longtime donors from investing in another Floridian, former Gov. Jeb Bush or Mitt Romney, who is seeking a third White House bid.

"Jeb Bush is going to be a very credible candidate. I think he's going to raise a lot of money," Rubio told The Associated Press. "He's got an extraordinary network of donors around the country, and I know he'll be a strong candidate if he runs."

It is too early to say how much the political advocacy network aims to spend on 2016 Republican election advertising. In 2014, the network aimed to spend $290 million on advertisements prior to the mid-term elections.

Koch political fundraising entities are entitled under the U.S. tax code to keep the identity of donors, and how much funds they give, secret.