The failure of the Trump administration thus far to staff up the executive branch is hurting the conservative policy agenda and thwarting the will of the voters.

And six Republican senators who asked Secretary of State Rex Tillerson to probe whether foreign aid is promoting a progressive agenda around the world just got an abject lesson in how.

They got their answer not from Tillerson or anyone around him, but from a mid-level career official at the Bureau of Legislative Affairs, Executive Secretary Joseph E. Macmanus. He pretty much told the senators to take a hike.

The six — Mike Lee (R-Utah), Bill Cassidy (R-La.), Ted Cruz (R-Texas), Jim Inhoffe (R-Okla.), David Purdue (R-Ga.) and Thom Tillis (R-NC) — had written Tillerson in mid-March requesting an investigation into whether State and the US Agency for International Development were using taxpayer money to support a raft of progressive causes with no clear national-security interest.

They also asked him to investigate how USAID was working with groups funded by billionaire George Soros “to push a progressive agenda and invigorate the political left.”

As an example, the senators mentioned how one such group pushed for reforms in Albania that some national leaders feared were “ultimately aimed to give the prime minister and left-of-center government full control over judiciary power.”

But Macmanus didn’t even acknowledge the request for a probe. It was just an outright defense of USAID’s work, with sentences like, “The Department of State’s foreign-assistance programs are rigorously designed, implemented and monitored to ensure that they are based on core American values.”

In other words, we know what we’re doing, you don’t.

It added at the end, for good measure, “We continually review US foreign-assistance programs, including advancing democracy, human rights and government assistance, to ensure the efficient and effective use of resources are aligned with US national interests and administration priorities. We hope this information is helpful.”

The exchange has left at least some of the senators convinced that the scarcity of political appointees at State and other departments has left career bureaucrats running the government.

They’re right. Of 553 key positions in the executive branch that require Senate confirmation, only 22 have been confirmed so far, according to the Partnership for Public Service. And it’s not just because the Senate is dragging its feet. There are 44 nominations awaiting confirmation and a whopping 488 awaiting nomination.

Ordinarily, congressmen from the same party as the administration, or their staff, can ring up political appointees who are sympathetic to their policy proposals. In this case, they might have been able to lobby for Tillerson to take a personal interest, or for someone else, say an assistance secretary or a deputy assistant secretary, to help get the investigation started.

Whether you love or hate Trump, it’s clear the policies that won the election on Nov. 8 aren’t being implemented.

Trump ran, among other things, on making national-security interests the first (and only) grounds for policy making and on the preference for national sovereignty over global governance. He cheered ­Brexit and encouraged other European states to follow the UK’s lead.

Soros’ Open Society Foundation and network of groups does some good in some places — by fighting Vladimir Putin’s bullying of Ukraine, for example. But Soros also supports worldwide many things conservatives find repugnant, such as the legalization of prostitution, the drug trade and abortion, and the demonization of Israel.

And Soros supports, above all, the expansion and strengthening of the types of international organizations that would limit the ability of nation states to act — the types that are anathema to Trump and his entourage.

The senators wrote that not only do many USAID and Soros activities lack a clear national-security purpose, but they can undermine efforts to build international relations that benefit America.

Sen. Lee warned that siding with the left would “ostracize many foreign citizens who have traditionally supported strong relations with the United States. Such division allows aggressive opportunists like Russia space to operate and cause further damage.”

It’s long past time Republican senators were able to get a sympathetic voice at the other end of the line at a Republican-run State Department.

Mike Gonzalez is a Heritage Foundation senior fellow for national security.