Charles Koch seems unimpressed with GOP field

Republican presidential contenders hoping to win one of the most coveted endorsements of the 2016 contest got a bit of bad news Tuesday morning.

Billionaire industrialist Charles Koch still isn't endorsing a presidential candidate and doesn't seem that excited about his choices.

In an interview on MSNBC's Morning Joe, the publicity-shy industrialist said he's long "been discouraged" by politicians who have failed to curb government spending once elected. Asked whether he sees a candidate in the 2016 Republican field who could advance his limited-government, free-market agenda, Koch said: "Not in great measure."

"I'm trying to be diplomatic," he added, laughing.

Koch said he's "not going to publicly comment on any candidate."

Charles Koch and his brother, David Koch, sit at the center of a vast policy and political network with enormous influence in Republican Party circles. Earlier this year, Charles Koch told Paste BN that the network was taking a close look at five contenders -- former Florida governor Jeb Bush, former Kentucky Sen. Rand Paul, Texas Sen. Ted Cruz, Wisconsin Gov. Scott Walker and Florida Sen. Marco Rubio. At the time, Koch said the group could back several or none of those contenders.

The Republican presidential race has proved unpredictable. Two political outsiders -- billionaire developer Donald Tump and Ben Carson -- now lead the polls. Paul is struggling to get attention, and Walker dropped out after lackluster debate performances and money struggles.

Koch's reluctance to endorse doesn't mean he won't have a say in politics.  He said he now expects his organization to spend about $250 million in elections in 2016.

"I expect something in return," he said. "I would love to have the government stop this corporate welfare. That's what I want."

Koch, who also appeared on the show with his brother, is in the midst of a publicity blitz to promote his new book, Good Profit.