Top Republican political leaders aren’t the only ones shunning their party’s presidential nominee — a vast number of highly skilled managers and policy experts, veterans of recent GOP administrations who would normally be expected to fill key positions for a new White House, are also vowing to sit out a Donald Trump presidency.

And while the failure of the two Presidents Bush or House Speaker Paul Ryan to endorse the presumptive nominee carries political consequences, the absence of policy veterans in a new administration would have a substantive effect on the running of government.

Politico interviewed nearly five dozen Republicans over the past two weeks — people with experience working in government and who understand how Congress can enact, or shred, a new president’s agenda — and heard the same sentiment expressed repeatedly. If Trump doesn’t change his tune or extend much longer olive branches, many of these government veterans say they intend to cede highly coveted administration posts to less-experienced competitors.

“I would never serve in a Trump administration,” said James Capretta, a former Office of Management and Budget official under George W. Bush. “The person at the top is unfit for the presidency. He’s made that very clear with his behavior.”