Republicans are growing concerned that the staffs of Donald Trump and Mike Pence are starting to feud, the latest trouble to hit a White House that has spent months battling crisis after crisis.

They worry that any rift could be delaying decisions, distracting aides from their already stalled legislative agenda and could lead to more infighting and leaks, problems that have plagued the White House since Inauguration Day.

A half-dozen Republicans, including four who advised or worked for Trump’s campaign or transition and are still in contact with their former colleagues, said they think the two sides are talking less, disagreeing more and occasionally bad mouthing each others’ bosses. One said the staffs are “walled off” from each other. Several of the Republicans asked to not speak publicly because of the sensitivity of the situation.

“There is clearly tension between the two staffs,” a former Trump adviser said. “There’s so much internet chatter. That’s going to fuel the animosity.”

Republicans say it’s only natural that some of the president’s aides are reconsidering who they can trust as the White House continues to reel from an undisciplined president and multiple inquiries into whether Trump associates joined Russia in meddling in the presidential election.

“The administration doesn’t know who to trust,” Republican strategist Michael Steel said. “When you’re under attack the circle tightens.”

At the same time, Republicans say, some of the vice president’s aides say they are frustrated over Trump’s many self-inflicted wounds, some of which the conventional and even-keeled Pence is forced to try to explain away as he looks to smooth over hurt feelings with members of even his own party.

“Trump does something and Mike Pence has to do cleanup,” Republican strategist Doug Heye said. “That can be very frustrating for staff.”

On Thursday, the vice president’s chief of staff Josh Pitcock resigned after just months on the job, saying he wanted to leave government work following a dozen years with Pence. He will be replaced in August by another long-term aide, Nick Ayers, who will lead a staff of about 50 or so who work in the building next to the White House, alongside some of the president’s staff.

Spokespeople with the White House and the vice president’s office, which have separate communications staffs, deny there are any problems between their offices and point out none of the people who worry about a potential rift between the staffs are actually in the White House. They say the White House and vice president’s office they work together hand in hand every day and if anything the two sides have grown closer since the start of the administration.

Members of the two staffs meet together regularly, they say. Trump and Pence scheduling and communications aides meet daily while the two chiefs of staffs meet several times a week.

Marc Lotter, Pence’s press secretary who worked on the campaign, said after Pence was tapped by Trump to be his running mate their teams were set up as mirror images of each other to make working together easier.

But during the presidential race, some of those who worked on the campaign said it was clear that some Pence aides did not like Trump, a brash businessman-turned-reality-TV-star who many rank-and-file Republicans opposed. After the election, some of those same aides had to be persuaded to work for Pence because it meant working for Trump.

In recent weeks, at least two of Pence’s mid-level aides appeared delighted that Trump found himself facing the unpredictable, back-to-back testimony of former FBI Director James Comey and Attorney General Jeff Sessions, according to a second former adviser in contact with both the Trump and Pence staffs. “It doesn’t cause them any discomfort when the president gets bad news,” a former campaign official said.

Presidential running mates and their staffs often clash as the two groups jockey for power and autonomy. But, Republicans say, the situation has gone beyond the normal tensions.

No single incident led Republicans to think the two staffs are growing apart, but they say the situation has gradually worsened in recent weeks as rumors flourish about who’s up and who’s down.

“If tensions are going on between the vice president's staff and the president's staff, it's simply because everyone is jockeying for positions, trying to find relevance, making sure they're not getting fired,” a second former campaign official said. “There's a lot of rumors, ‘this person is going, that person is going.’ It's just that there's a lot of jockeying going on.”

Yet all the sniping behind closed doors hasn’t extended to the president and vice president, the same Republicans say.

Trump continues to give Pence a significant role that has him at the president’s side every day as he assists with some of the biggest foreign and domestic policies, including health care, tax reform and other issues on Capitol Hill, where the vice president served in House leadership and was known for getting things done. In recent days, he has been meeting with individual senators about a proposed Senate health care overhaul.

Trump and Pence — a political odd couple who have vastly different styles and policies — didn’t know each other well before Trump tapped Pence to be his running mate. But Trump, a political novice, has relied on Pence in ways that other modern presidents haven’t, as he started to navigate the nation’s capital by using Pence’s connections, conservative credentials and knowledge of policy.

Trump, who has been known to lash out at staff, hasn’t taken the same tack with Pence, even when headlines refer to the possibility of a “President Pence.” The two men speak every day, multiple times a day, even when one of them is traveling, aides say. “I think the relationship at the top is solid,” the first campaign aide said.

Pence has never strayed from his role as loyal soldier, constantly supporting and praising Trump, and explaining what Trump meant in interviews, at events and, of course, Twitter.

“President Trump is fighting for each one of you every single day,” Pence told a group of builders and contractors last week. “The man is a fighter — like nobody I ever met.”

A second former Trump adviser predicts Pence and his most senior aides will remain loyal because they understand that the president has helped shape a new political realignment that could benefit Pence in eight years if he runs to succeed Trump.

“If this realignment is real then he is absolutely guaranteed Trump’s third term,” the former adviser said. “All they want to do is strengthen that. They see the broader picture.”

Others say many of Trump’s top staffers worked for Pence and remain close to him and would never let the disagreements get in the way of their work. A couple of the higher-profile examples: Trump counselor Kellyanne Conway served as Pence’s pollster before the presidential campaign, and Director of Legislative Affairs Marc Short worked for Pence when he was in the House. Short regularly travels with Pence even now.

The staffs of President Barack Obama and Vice President Joe Biden were friendly in part because the two men considered each other as close as “brothers,” a rarity in the White House.

Former White House Press Secretary Josh Earnest said that Obama and Biden got along so well, even though their ages, backgrounds and experiences were vastly different, because their relationship was built on trust. He surmised any disagreements between Trump and Pence staff must have stemmed from Trump allowing Pence to utter a statement about now fired National Security Adviser Michael Flynn that he knew wasn’t true. Trump fired Flynn for lying to Pence, but it came two weeks after it became public.

“It would make sense that the vice president and his team, based on that episode, are mistrustful of President Trump and I’m sure they’ve made that known to the President’s team,” Earnest said. “And that lack of trust is going to take a toll on their relationship as it would any relationship with a president and vice president.”