It took less than a day for Tim Walz to start unraveling: It turns out Kamala Harris’ running mate lied for years about leaving the National Guard with the high rank of Command Sgt. Major.

In fact, he was demoted after bugging out when his unit was called up to serve in Iraq in 2005.

That’s the opposite of real leadership, and all too fitting for the Harris-Walz ticket.

He “slithered out the door,” charge two of his former Guard colleagues, Command Sgts. Major Thomas Behrends and Paul Herr (both now retired), leaving the unit “hanging without its senior Non-Commissioned Officer, as the battalion prepared for war.”

Yes, Walz had every legal right to leave when he did, after two decades of peacetime service, but countless other Guardsmen (and reservists) didn’t bow out when the call came.

More: Despite multiple claims to the contrary over the years, Walz never served in combat.

Yet he keeps mocking his GOP counterpart, J.D. Vance — who did come under fire as a Marine in Iraq.

Kudos to Vance for trying to confront Walz and Kamala Harris on a Wisconsin tarmac Wednesday — and for needling his opponents and the press over Harris’ teleprompter-only record since moving to the top of the Democratic ticket.

“I also thought you guys might get lonely because the vice president doesn’t answer questions from reporters and hasn’t for 17 days,” he told the traveling campaign reporters.

And: “Have they given you guys an explanation for why she won’t take questions from reporters?”

That gets directly to Harris’ leadership failures: No one can point to anything she’s achieved as vice president, especially in her role as “border czar.”

Nor has she outlined any ways in which she’ll break with Joe Biden’s disastrous policies on the economy or the border — the voters’ top two issues.

Heck, she still has to fill in any policies on her campaign website.

And four-minute off-the-record “gaggles” on Air Force Two don’t count.

Meanwhile, Vance and Donald Trump take questions regularly.

They’re not afraid to face the press and Trump has never failed to confront a challenge facing the nation.

The Harris strategy seems to be to coast to Election Day on not being Biden, hoping the voters keep treating her as a fresh face — the only two factors that explain how she’s narrowed the Trump-Vance lead in the polls.

With the national media largely in the tank, this may buy her another week or two, but the voters aren’t that stupid.

Walz isn’t getting away with lying about his service, and Harris won’t get away with hiding forever from live interviews and tough questions.

Americans recognize leadership — and its opposite.