Mitt Romney foreign policy spokesman Richard Grenell has left the presidential campaign after less than a month, citing “hyper-partisan discussion of personal issues.”

Grenell, who led United Nations communications for the Bush administration, is openly gay and was a target of criticism from conservatives in the Republican camp. He also made brash remarks on Twitter about Rachel Maddow and Callista Gingrich and was benched in a big foreign policy week in the presidential campaign.

In a statement, Grenell said his “ability to speak clearly and forcefully on the issues has been greatly diminished by the hyper-partisan discussion of personal issues that sometimes comes from a presidential campaign.”

Romney campaign manager Matt Rhoades said in a statement that the campaign urged Grenell to stay on. “We are disappointed that Ric decided to resign from the campaign for his own personal reasons,” said Rhoades. “We wanted him to stay because he had superior qualifications for the position he was hired to fill.”

Grenell was tapped to speak for the campaign on national security and foreign policy.

Politico noted Grenell's first Twitter message after joining the campaign said "not all gays" are "big government liberals."

In one widely circulated tweet, American Family Association issues director Bryan Fischer said, "Romney picks out & loud gay as a spokesman. If personnel is policy, his message to the pro-family community: drop dead."

After eight years in the Bush administration at the U.N., Grenell set up PR shop Capitol Media Partners in Los Angeles.

The Washington Post and New York Times reported that the campaign had cut Grenell out of the loop on some issues because of conservative pressure. The Post noted his obvious absence in a week dominated by foreign policy on the anniversary of Osama bin Laden’s death.

“Why wasn’t [Ric] the spokesman in the last couple of days, when foreign policy was paramount?” Bush White House press secretary Ari Fleischer wondered in the Post. “That’s the piece I don’t understand.”