Conservatives lash out after Trump endorses Dr. Oz: 'They played him. Again.'
President of the United States Donald Trump speaking at the 2017 Conservative Political Action Conference (CPAC) in National Harbor, Maryland. (Gage Skidmore/Flickr)

Donald Trump's once iron-clad grip on the Republican Party appears to have weakened as prominent conservatives are openly griping about his endorsement of Dr. Mehmet Oz in the GOP primary for U.S. Senate in Pennsylvania.

Joel Pollack, the senior editor-at-large at Breitbart, said Trump could lose the support of his base over the endorsement.

"This endorsement could divide MAGA in the only way that matters: he could lose America First conservatives over it," he wrote.

Prominent far-right blogger Erick Erickson blamed Trump's staff for the endorsement.

"It’s like Donald Trump’s staff is sabotaging Trump by convincing him to make the worst possible endorsements," he tweeted.

Rep. Mo Brooks (R-AL), who was un-endorsed by Trump in his Senate campaign, retweeted Erickson with his own thoughts.

"This is happening because Trump’s surrounded himself by staff who are on McConnell’s payroll & hostile to the MAGA agenda. Everybody telling Trump who to endorse in primaries works for The Swamp," he charged. "They played him. Again."

Pulitzer Prize-winning New York Times journalist Maggie Haberman was surprised by Brooks' tweet.

"The ongoing need to blame everyone but Trump for Trump’s own choices is striking given that Brooks, who Trump dumped, is one of those doing it," she wrote.