President Trump has repeatedly asserted that "Mexico will pay" for his proposed southern border wall – but he's also said the U.S. will be reimbursed by Mexico after building it with taxpayer funds. (Peter Stevenson/The Washington Post)

Senate Majority Leader Mitch McConnell was asked by Politico's Jake Sherman and Anna Palmer on Thursday morning whether he believed that Mexico would, ultimately, foot the cost for the border wall President Trump wants built on our southern border.

“Uh, no,” was McConnell's blunt response, according to CNN's Manu Raju.

That's the general feeling within the GOP political establishment when it comes to the prospect of Mexico paying the estimated $12 billion to $15 billion cost of the border wall. But it's not something they usually say aloud because Trump continues to insist — and insist — that Mexico will, eventually, pay for the costs of the wall.

Under Trump's theory, the federal government will initially allot the billions needed to build the wall. But then, because he is such a good dealmaker, he will make clear to Mexico that if it wants to keep exporting goods to America without a significant tariff, then it had better reimburse us.

“When you understand that Mexico's economy is dependent upon U.S. consumers, Donald Trump has all the cards he needs to play,” Rep. Chris Collins (R-N.Y.), a prominent Trump supporter, said on CNN earlier this year. “On the trade negotiation side, I don't think it's that difficult for Donald Trump to convince Mexico that it's in their best interest to reimburse us for building the wall.”

That's a long shot — to say the least. Not only are U.S.-Mexico relations not in a good place at the moment, but there is also the possibility that the 2018 Mexican presidential election could produce a candidate even less inclined to deal with Trump. Andrés Manuel López Obrador, who has been outspoken about his issues with Trump and the United States, is seen as the race's front-runner at the moment.

The most likely outcome of Trump's wall plan is that U.S. taxpayers will foot the bill for it, Mexico — maybe! — pays back a pittance of the overall cost, and Trump declares victory even though he has added significantly to the deficit to build the wall.

That's striking given that Trump heads a party that made a name for itself over the past several decades on its commitment to financial restraint and responsibility. (Remember that during the Obama administration, congressional Republicans would often demand things like disaster relief be fully paid for so as to keep the government's deficit from growing larger.)

It is, of course, possible that Trump pulls off a miracle and convinces Mexico — despite the country's repeated denials — that it makes sense to pay for the wall. Trump was, after all, never supposed to win the Republican nomination, and no one thought he even had a chance in the general election against Hillary Clinton. And yet, here we are.

But the prevailing sentiment within Washington Republican circles is that a scenario like that coming to pass is very, very unlikely — meaning that, at the end of the day, the wall's construction will be paid for by taxpayers. McConnell's blunt response makes that belief plain. If congressional Republicans go forward with a wall-funding plan, they won't be able to argue they didn't know what they were getting themselves into.