The email, signed by 2016 Committee National Chairman John Philip Sousa IV, said that the race is still "in flux" but if Carson isn't on the ticket, "The Democrats will win the White House and the America we love will disappear."
Sousa said front-runner Donald Trump
and Sens. Marco Rubio
and Ted Cruz
can't win without Carson, who has thus far lagged behind the field in the early nominating states.
"Trump, Rubio and Cruz are all destined to lose in 2016 because without Ben Carson on the ticket, they will lose the African-American vote," he wrote.
He added that's why it was important to keep Carson, who is languishing at the bottom of polls and delegate count, in the campaign.
"The demographics of America have changed dramatically, and that is why Ben Carson must stay in this race," Sousa wrote. "He may not win the GOP nomination, but he still holds the winning hand in this political poker game. If Ben Carson is on the ticket, either as president or as vice president, we can win the White House by winning upwards of 25% of the black vote and 35% of the Hispanic vote."
Sousa did not offer any data to back up his claim in the email, but later told CNN in a subsequent interview it was based on internal polling for Carson and former 2012 candidate Herman Cain
. Sousa said it was also because of Carson's message and life story.
"There is no doubt in our mind that Dr. Carson can get a substantially higher percentage (than Cain), mostly because of his story," Sousa said. "We think that will be inordinately attractive to the black voters."
Carson's campaign said it does not work with the super PAC "or have any influence over their message." Campaigns are barred by law from coordinating with supportive super PACs.
"Dr. Carson intends to represent all Americans, regardless of race, gender, or creed, and his message of faith, integrity and common sense leadership is similarly resonating across all demographics," said A. Larry Ross, the campaign's communication director said in a statement. "He is committed to pressing on with his campaign as long as he continues to receive donations and support from 'We the People.' "
Carson raised eyebrows Tuesday when he said President Barack Obama was "raised white" and that his own election to the White House would mark a significant step for African-Americans.
"Like most Americans, I was proud that we broke the color barrier when he was elected, but I also recognize that his experience and my experience are night-and-day different. He didn't grow up like I grew up by any stretch of the imagination," Carson told POLITICO this week. "He's an 'African' American. He was, you know, raised white."
The pro-Carson super PAC has also had its share of problems, including a mass defection of its staffers in New Hampshire to Cruz's rival campaign ahead of the primary there
. That exodus included the group's executive director.
Sousa told CNN, however, that the staff departures were minor and that the executive director, Sam Pimm, was asked to leave.
"They were very, very low-level intern types that had zero impact on what we were doing," Sousa said of the staffers. "And in terms of the executive director, we fired him, because he was worthless."
Reached for comment, Pimm said he resigned.
"I tendered my resignation due to disagreements over personnel," Pimm said.
Pimm also questioned Thursday's fundraising email, saying Carson staying in the race only benefits Trump. He added he hadn't seen any polling that Carson was the leading choice for vice president.
"The idea that a Republican cannot win the White House without Ben Carson on the ticket is ... just plain crazy," Pimm said in an email.
Carson has four delegates in the Republican presidential primary compared with Trump's 82. He finished fourth out of five candidates in the Nevada caucuses with 4.8% of the vote.