Mick Mulvaney may not be on the way out from his acting chief of staff role anytime soon, but he’s undergoing a familiar ritual for Donald Trump’s advisers and staff: stories about how he’s falling out of favor. Politico’s Nancy Cook reports, “Trump has been snapping at his acting chief of staff with some frequency, and expressing greater frustration with him than usual,” and that the “president has asked people in recent months what kind of leadership they think Mulvaney is offering in the West Wing and the value he is adding.”

Trump also got annoyed with Mulvaney’s coughing: During an interview with ABC, the famously germaphobic president responded to Mulvaney’s coughs by saying, “If you’re going to cough, please leave the room. You just can’t, you just can’t cough.”

But while this type of treatment is normal for basically anyone in the White House outside of Trump’s nuclear family, it should not be surprising that Trump is souring on Mulvaney for more substantive reasons: When it comes to public policy, and especially budget policy, the two agree on very little.

Much like National Security Adviser John Bolton, Mulvaney is a publicly loyal and aggressive advocate for Trump who backs him on otherwise unpopular decisions like the government shutdown. But he also has deep disagreements with the president over basic issues on public policy, and he uses his influence to pull the White House toward his preferences — and then Trump pulls back when he realizes what’s going on.

Mulvaney looks at the federal budget as a list of programs whose ongoing funding should be explicitly justified against the preference for reducing overall domestic spending as much as possible in order to reduce overall government expenditure. President Trump, on the other hand, has no desire to cut deficits or incur bad press, and is more than happy to spend money on whichever constituencies he likes.

Mulvaney first came to Congress in 2011 as part of the Tea Party wave and quickly became identified as one of the most ferocious opponents of the Obama agenda and government spending in general, even going further than many of his colleagues in opposing increases to military spending.

In his roles as both the head of the Office of Management and Budget as well as chief of staff, he’s both overseen the creation of White House budgets that include drastic spending cuts and worked with Congress to pass spending bills that bear little resemblance to the hardline budgets his team produces.

This has led to some embarrassing moments for Trump, including when a budget proposal zeroed out the Education Department’s funding for the Special Olympics, which Education Secretary Betsey DeVos defended before Trump said he had “overridden my people” and scratched the cuts (which were unlikely to ever happen in the first place).

Mulvaney was also reportedly a key voice in convincing Donald Trump to re-embrace the Obamacare repeal by backing a legal challenge to the whole law earlier this year, forcing congressional Republicans to start talking about health care again just months after losing their majority in the House of Representatives.

While Mulvaney will defend cutting, say, the Community Development Block Grants and after-school programs as “compassionate” for the taxpayer, Trump has evinced no concern for growing deficits while in the White House and is more than happy to cut deals with Democrats that increase both domestic and military spending — and to back away from Mulvaney’s severe proposals when he gets bad press.

The question is less why Trump is starting to look skeptically at his chief-of-staff-cum-budget-director, but more how he got so much power and influence in the first place.