"I am not saying there is not going to be any support", for Pence if he his chosen as Trump's running mate, "but I am saying it would not be optimal for him", Perkins said.
Christie, 53, a tough-talking politician described as a political bruiser, already campaigned with Trump in Virginia on Monday.
Trump's vice presidential pick could be one of the most important decisions he makes on the campaign trail as he seeks to present a competent, steady wingman or woman to U.S. voters after a turbulent primary season during which his provocative rhetoric frustrated many conservatives.
"I would rather have the whole thing be on policy", Trump continued.
Trump knows Pence less personally than Gingrich and Christie, who have been vital behind-the-scenes advisers to the candidate.
Tony Perkins, president of the Family Research Council, said that Pence would have been a good choice had he not amended RFRA in 2015.
We've now entered the full Hunger Games portion of the pre-VPannouncement, with both Mike Pence and Newt Gingrich meeting privately todaywith Donald Trump and his son, daughter and son-in-law.
Trump told The Wall Street Journal on Tuesday he is looking for a "fighter skilled in hand-to-hand combat" as his second-in-command, but hadn't seen enough of Pence to measure his fight.
With the Republican National Convention just days away in Cleveland, Indiana has become the center of the vice presidential discussions with another potential Trump running mate Alabama Sen. The governor introduced Trump at a rally in Westfield, Indiana, Tuesday night.
But he concluded that "reading Donald Trump's mind is not the easiest thing to do".
Trump has also said he is considering other candidates who have not gotten much media attention.
Trump on Wednesday morning had breakfast at the Indiana Governor's Mansion with Pence.
Governor Christie remains on the short-list to run alongside Donald Trump on the Republican Party ticket, but he was not among the candidates who met with the presumptive nominee Wednesday as he nears a decision.
"Mike is not going to go and defend Trump the way he needs it - the way a Newt or a Christie would, or even the way a Sessions has", the adviser said. He was House speaker when Democrat Bill Clinton was president in the 1990s, and they achieved welfare reform, among other legislative achievements.
Asked if he is open to being her running mate, Sanders said, "I doubt that will happen".