During a speech in Youngstown, Ohio, Republican presidential nominee Donald Trump outlined some of his plans to defeat the Islamic State and protect the United States. (Sarah Parnass/The Washington Post)

Donald Trump gave a self-described major speech Monday focused on how he would deal with the threat posed by the Islamic State. The centerpiece of his speech was a plan for "extreme vetting" of people who want to enter the United States. The address contained few details, designed instead to make the case he will be tougher, stronger and more aggressive in dealing with the threat posed by Islamist terrorists than either President Obama or Hillary Clinton.

Here's the problem: Lots and lots of what Trump said Monday about his foreign policy views stands in direct contrast to what he has said about those same topics in the past. From Iraq to Libya and back, Trump is adopting positions that are 180 degrees from what he said a few years ago.

The crack team of producers at "Morning Joe" — Jesse Rodriguez and his cohorts — put together a stunning 83-second clip that shows exactly how much Trump is fibbing about his past positions. Here it is:

Pretty devastating, right?

(Side note: For a terrific timeline of all that Trump has said on Iraq, check out this Fact Checker post.)

The simple fact is that Trump's views on Iraq as well as on a number of other foreign policy issues are at odds with what his positions were just a few years ago. That he says they aren't is, well, wrong.

Trump's tendency to rewrite history in ways that are favorable to him and to rework — to be kind — his policy stances to fit the moment are two pillars of his campaign to date. He knew better than all the professional politicians about everything — and said so at the time! The facts, however, don't bear that revisionism out.

For Trump's core supporters, none of this matters. The corrupt media is saying he is misrepresenting his past views? That's because they are afraid of him winning!

But as we've seen in state and national polling over the last six weeks or so, Trump's core base of supporters is just not big enough to keep him competitive against Clinton. And his insistence on rewriting history even when he knows that video like the one above exist to debunk his claims, further erodes any attempt to build credibility with those voters who view him skeptically.