Rev. Rick Warren strongly denied rumors GOP presidential candidate John McCain had “cheated” at a political forum he hosted at his church Saturday evening.

“That's absolutely a lie, absolutely a lie,” Warren said in an interview with BeliefNet. “That room was totally free, with no monitors--a flat out lie.”

Warren said Barack Obama’s supporters who are making the accusation McCain had knowledge of the questions Warren asked him ahead of time are “dead wrong.”

“That's just sour grapes,” Warren said. “They both did fantastically well. The only question he knew, I gave them the first question and I was changing the questions within an hour [before the forum began.] I talked to both of them a week before the debate and told them all the themes. I talked personally to John McCain and I talked personally to Barack Obama. I said, 'We'll talk about leadership, talk about the roles of government,' I said I'd probably have a question about climate change, probably a question on the courts. I didn't say, 'I'm going to ask which Supreme Court justice would you not [nominate]. They were clearly not prepared for that.”

Warren’s forum was the first time McCain and Obama both appeared at a presidential event. Warren questioned each candidate separately for an hour each. Obama’s session was held first, followed by McCain’s. Warren promised McCain was contained “in a cone of silence” during Obama’s allotted time to ensure McCain would not hear the questions ahead of time. Both candidates were asked the same questions.

Many political analysts agreed McCain outperformed Obama at the event, largely because of his directness in answering Warren’s questions, which ranged from abortion, to marriage, to poverty to social justice issues.

MSNBC’s Andrea Mitchell said on Meet the Press Sunday, “The Obama people must feel that he didn't do quite as well as they might have wanted to in that context, because that -- what they're putting out privately is that McCain may not have been in the cone of silence and may have had some ability to overhear what the questions were to Obama.”

“He seemed so well prepared,” she added.

The McCain campaign pushed back hard against MSNBC for perpetuating the rumor Monday morning. McCain Campaign Manager Rick Davis sent a letter to the NBC News President Steve Capus that said, “"Instead of examining the Obama campaign's spin for truth before reporting it to more than 3 million NBC News viewers, Andrea Mitchell simply passed along Obama campaign conspiracy theories.”

Davis also requested a meeting “with you as soon as possible to discuss our deep concerns about the news standards and level of objectivity at NBC.”