Sonny Perdue, President Donald Trump’s nominee to serve as agriculture secretary, has not yet been confirmed, and nobody knows why.

It’s not that Democrats are obstructing his confirmation — since changes to the Senate’s filibuster rule, they can’t block a Trump nominee unless they recruit three Republican “no” votes. And in the case of Perdue — unlike, say, Education Secretary Betsy DeVos — they aren’t trying to do this. Nor are they resorting to extraordinary measures like the all-night debate that stalled Attorney General Jeff Sessions’s confirmation, or the committee walkouts that dramatized ethical issues hanging over the heads of Treasury Secretary Steve Mnuchin or Health and Human Services Secretary Tom Price.

The reason the Senate hasn’t yet approved his nomination is that he hasn’t actually been officially nominated yet. Paperwork hasn’t yet traveled down from the executive branch to the Senate, so no hearings have been scheduled, even though Perdue does not appear to be a controversial nominee.

Nobody knows what the problem is

Perdue’s nomination appears to be in limbo due to either the FBI background check or to financial conflicts of interest considered by the Office of Government Ethics. But it seems nobody is entirely sure whether there’s an actual problem, how serious the problem is, or whether the vetters are simply overwhelmed with other work.

"They don't seem to have a reason as to why his name hasn't come up," Iowa Republican Sen. Chuck Grassley told reporters back on March 2.

Trump put forward his initial round of nominees with less attention paid to vetting than has been traditional for recent presidents. Problems later arose that forced his nominees for secretary of the Army, secretary of the Navy, and secretary of labor to withdraw. In the case of labor nominee Andy Puzder, the issue was a mix of intense liberal opposition plus a considerable amount of scandal. The Army and Navy secretary nominees withdrew after deciding that there was no satisfactory way to resolve their financial conflicts of interest that they were personally comfortable with.

So it is conceivable that Perdue has run into a business interest problem or that something more scandalous has come up. But it’s also conceivable that the Trump administration’s delayed interest in vetting has simply things backed up. Perhaps the Agriculture Department is simply a low priority. Trump swept up votes in rural America, but his personal interests are in big city real estate development, and his trade protection agenda would be a disaster for American farmers.

It is so pathetic that the Dems have still not approved my full Cabinet. — Donald J. Trump (@realDonaldTrump) March 3, 2017

The truth is that nobody in Washington seems to know. Democratic Senate aides profess to be genuinely baffled as to what the holdup is. They are also somewhat uncertain as to whether Trump is deliberately lying when he says “the Dems” are blocking the confirmation of his remaining nominees (Puzder’s replacement as labor secretary, Alexander Acosta, also hasn’t been formally submitted) or is simply confused about what’s going on.

A not-very-controversial establishment Republican

Were he actually to be nominated, it seems like Perdue’s confirmation would be an easy one. Democrats are not going to commit to voting for Perdue before he’s even been nominated. But the Perdue pick very much follows in the mold of some of Trump’s less contentious nominations like Rick Perry at the Energy Department or Elaine Chao at transportation.

Meanwhile, agriculture issues are more dominated by interest group lobbying than by sharp partisan conflicts. Perdue is seen as reasonably well-qualified, coming from a farm background and having served eight years as governor of Georgia. And in general, Perdue’s outlook on issues is very conventional Republican Party fare. Additionally, Perdue has been a conventional Republican free trader for most of his career. Agribusiness interest groups have been counting on him to carry that torch into the Trump administration.

Bob Young, chief economist at the American Farm Bureau Federation — which likes Trump’s ideas on deregulation and tax cuts but disagrees with him on trade — voiced tremendous optimism about Perdue as a free trader in an NPR interview when he was first nominated: “He's run businesses on farm inputs — fertilizer sales, for example. [He’s] also run a business basically set up to promote trade of agricultural products.”

It’s also worth noting that Perdue was an early adopter of anti-immigrant politics in the GOP. As governor, he signed a law that imposed a harsh crackdown on undocumented workers back in 2006, when George W. Bush was in office and pushing for a comprehensive reform bill that would include a path to citizenship. But by 2010, Perdue was already warning that nativism had gone too far in some conservative circles, cautioning fellow Republicans to avoid a “gang-type mentality” and to make sure that “people of color and people who are not U.S.-born” feel welcome in the United States and in the Republican Party.

The machine is not that fine-tuned

It’s possible that the very farm-related businesses that made Bob Young optimistic are the problem, causing some kind of conflict of interest that Perdue hasn’t yet resolved in a satisfactory way.

It’s also possible that the problem has something to do with Perdue disagreeing with Trump on trade and immigration.

Early Trump picks were often made without regard to the nominee’s previous stances. Defense Secretary James Mattis, for example, was a proponent of the Trans Pacific Partnership, and Perry called Trump a “cancer.” But since settling into office, Trump has become increasingly concerned about leaks coming from inside the government and thus more focused on loyalty.

Whatever the problem is, the Trump administration has not conveyed any information about it to the public, to interest groups, or to allies on the Hill. Trump’s inaccurate March 3 tweet complaining that Democrats are blocking Cabinet nominees he hasn’t formally nominated has been his only recent commentary on the subject. Meanwhile, cattle trade groups have been reduced to writing public letters to the administration urging Trump to ask the Senate to act speedily on the nomination.

What nobody is saying is that whatever the holdup is, it has absolutely nothing to do with the senate.

Way back on February 9, the ranking Democrat on the Senate Agriculture Committee met with Perdue and issued a friendly statement saying she was looking forward to “having a confirmation hearing after the Committee receives the required documents.”

Four weeks later, the reality is that they still haven’t.