A Baptist pastor from Dallas who has endorsed Rick Perry introduced the Texas governor at a conservative forum on Friday in Washington, then later told reporters that Mormonism — the religion of Mitt Romney, Mr. Perry’s main rival for the Republican presidential nomination — was a cult.

The pastor, Robert Jeffress, a senior pastor of the First Baptist Dallas megachurch, said Mr. Romney was suspect on abortion and marriage, a conservative of convenience. Then he went on to say that it is the official view of the Southern Baptist Convention that Mormonism is a cult and that this was a factor in his decision to endorse Mr. Perry.

“Mormonism is a cult,” Dr. Jeffress said. “Mitt Romney is not a Christian.”

(Baptists and many other evangelical denominations consider Mormonism not authentically Christian because Mormons add things to the sacred scriptures. But many theologians also say that this distinction does not apply to politics, and that they would vote on the issues, not religion.)

Dr. Jeffress said that he had not discussed this issue with Mr. Perry, and that he had no idea what the Texas governor thinks.

Mark Miner, a spokesman for Mr. Perry, said the governor did not believe that Mormonism was a cult, and added, “The event organizers chose who introduced the governor.”

“The governor doesn’t get into the business of judging other people’s hearts or souls,” Mr. Miner said. “He leaves that to God.”

Dr. Jeffress said that the Constitution allowed anyone to run for president, but that as a citizen, he wanted a true Christian.

“If you vote for Romney, don’t be under the illusion that you voted for a Christian,” he said. “I’m not saying that Romney is not a good person, but that he will not be saved.”

Even so, Dr. Jeffress said, if Mr. Romney were the nominee, “I probably would hold my nose and vote for Romney.” He added, “I’d rather vote for a non-Christian who embraces Christian values than a professed Christian who governs by unbiblical principles.”

But he also said he believed that if Mr. Romney were the nominee, “Barack Obama will be re-elected.”

He predicted that many evangelicals would tell pollsters that they did not care about Mr. Romney’s religion, because they did not want to appear bigoted, but that in the privacy of the voting booth, they would not vote for a Mormon. In a general election with Mr. Romney as the candidate, many would stay home, he said.

Dr. Jeffress did not mention Mormonism during his introduction, in which he combined lavish praise for Mr. Perry’s record on abortion, marriage and the economy with questions about Mr. Romney’s sincerity.

And Mr. Perry’s speech? It was well received, but perhaps now overshadowed.

Richard A. Oppel Jr. contributed reporting.