Now, says everyone, is the time that Donald Trump's train needs to be stopped. Everyone says stand on the tracks if you need to!

"GOP leaders, you must do everything in your power to stop Trump," blares the headline of a Washington Post editorial. Here's the key bit:

Absent an extraordinary effort from people who understand the menace he represents, Donald Trump is likely to be the presidential nominee of the Republican Party. At this stage, even an extraordinary effort might fall short. But history will not look kindly on GOP leaders who fail to do everything in their power to prevent a bullying demagogue from becoming their standard-bearer.

Fair enough. The problem with the "stop Trump now" movement, of course, is that it assumes that (a) Trump can be stopped and (b) that the party elders, poobahs and gray beards can do it. I'm skeptical about that first idea but totally certain on the second: The establishment -- whether that's defined by Republican National Committee Chairman Reince Priebus, Senate Majority Leader Mitch McConnell (Ky.) or House Speaker Paul D. Ryan (Wis.) -- can't suddenly press a switch or pull a lever to stop Trump.

How am I so sure of that? Because if the establishment could have stopped Trump, it would have done so months ago. The "dump Trump" sentiment appears to be reaching critical mass now, but the truth is that lots of smart people in the Republican Party knew in the fall that Trump could be the nominee and that his nomination could cause major problems for the GOP, not only in the presidential race but also in down-ballot contests, too. There were disorganized efforts back then -- mostly led by former Florida governor Jeb Bush -- to disqualify Trump for his past less-than-conservative views and his penchant for just saying whatever pops into his mind.

That didn't work. Trump's supporters loved him for his willingness to say whatever whenever and own it. They didn't trust longtime politicians, such as Bush, who they viewed as jealous of Trump's successes -- in the 2016 race and in life. The Trump army was built on a common belief that the Republican political establishment had screwed everything up by capitulating to Democrats and accepting half-measures because they are bad negotiators. The idea that one of those reviled members of the political establishment could somehow lead an effort to peel away supporters from Trump just doesn't make any sense.

Read all of the "stop Trump" stuff being written right now. You'll see the one thing it all lacks is a "how." How, exactly, do you stop a candidate who has run without any support from the establishment (elected officials, major donors, etc.) and who has won the past three contests by double digits? Who is the person -- or persons -- who can stand in front of that train and scream "stop" without getting run down? And, if such a person exists -- breaking news: he or she doesn't -- what, exactly, would such a person say to halt Trump or slow his momentum that Trump hasn't already said or done himself? Trump has said 10 things in just the past few months that would have crippled or even ended other candidacies. Yet not only does it not hurt him, it seems only to make him stronger.

If Trump could have been stopped by the establishment, it would have done it over the summer, when he announced his candidacy and was generally viewed as a sideshow. Savaging him as a thrice-married, weakly committed conservative might have worked then. But eight months removed, the time to simply stop Trump has passed.

That doesn't mean Trump will be the GOP nominee. Things change in politics -- often rapidly. But the only way that change happens is if voters in states holding primaries on March 1 and March 15 make it happen. Nothing that comes from official Washington or bears the whiff of the party establishment can stop Trump. Trying to would make him only more likely to win.