There is a humanitarian and security crisis at our nation’s southern border. Our country is threatened by the inflow of drugs and criminal aliens. Career border security experts continue to express strong support for physical barriers.

The simple truth is these walls and fences work. In fact, the Trump administration reports that in four border sectors where physical barriers were recently built or upgraded, illegal traffic dropped by more than 90 percent.

The statistics show and the experts agree that we need increased resources to protect our borders. But for some reason, Washington Democrats are rejecting these facts. Instead, they’re prolonging this partial government shutdown and leaving hundreds of thousands of federal workers to miss paychecks.

Adding to the absurdity is Democrats’ own history with this issue. In 2006, then-Sen. Barack Obama joined with then-Sen. Hillary Clinton, Sen. Chuck Schumer, and several other well-known Democrats when they all voted to authorize about 700 miles of physical barriers under the “Secure Fence Act.” That’s not the last time Democrats have supported walls. In fact, more than 80 percent of Senate Democrats voted for $1.5 billion for border barriers just last year.

Unfortunately, in the Democrats’ never-ending march to the left, they’re now abandoning long-held, bipartisan principles that most Americans support, like the need protect our country’s borders. New Speaker of the House Nancy Pelosi even recently described a barrier as “an immorality” and decided that opposing President Donald Trump comes before the security of our borders.

“An immorality” to protect our sovereign nation’s borders from drug smuggling and human trafficking? She couldn’t be more wrong.

The reality is, the Trump administration requested funding for the same kinds of physical barriers that the Obama administration was proud to build: Fencing with spaced slats that allow visibility, made with reinforced steel. Furthermore, they’re the same kinds of barriers that Customs and Border Protection experts have told us actually produce real results.

You can call them walls. You can call them fences. You can call them steel slats. What they really are is effective.

During the Obama administration, everyone supported a wall. Now, during the Trump administration, the Democrats decry the concept of any physical wall on the southern border as “an immorality.”

Pelosi’s argument becomes even more unpersuasive when you consider the cost of the president’s border security proposal. Democrats would rather continue this partial government shutdown than agree to an additional investment of approximately one-tenth of one percent of federal spending.

Just like many Kentuckians, I can’t think of a credible reason for the Democrats’ massive flip-flop on the need for border security. Instead, we’re left to believe that the Democrats are operating purely on political spite directed at President Trump. Why else would they rather have a partial government shutdown drag on for weeks than continue to support border security? Why else would they plug their ears and refuse to listen to the experts on the ground?

I agree with former-President Obama’s own Border Patrol chief, who stated recently, “I cannot think of a legitimate argument why anyone would not support the wall as part of the multilayered border security issue.”

Democrats are trying to convince the country that the federal government simply cannot reopen. They want you to believe they cannot negotiate with the president and the sky would come crashing down if we invest one one-thousandth of federal spending in proven border security solutions. And, they’d like you to forget that their own party used to support these same barriers.

Let’s call this what it is. It’s a partisan flip-flop that is not based in principle or in evidence, but solely in the fact that President Trump is in the White House.

Along with my Republican colleagues, I am proud to support the president’s commonsense request. The experts on the ground, who actually risk their own safety to secure our nation, support it. In 2006, then-Senators Obama and Clinton and the current Senate Democratic leader supported it.

Border security still matters, and American families still deserve safety. Speaker Pelosi’s posturing isn’t how you make serious policy, and her allies’ partisan tantrums are no way to govern.

The Democrats need to get serious about their responsibilities, seek treatment for their brand-new partisan allergy to border security, sit down with the president, and negotiate a solution that works for everyone. That is the only way to move the country forward.

Sen. Mitch McConnell, R-Ky., is the Senate Majority Leader.