Washington (CNN) President Donald Trump won the White House in 2016 due, in large part, to his willingness to play on deep-seated fear of the other. "They" were invading America,Trump argued. "They" were challenging "our" values, changing the face of America in ways that were deeply damaging to the country.

In ways large and small, Trump has continued to blow the dog whistle as President -- insisting that on everything from immigration to trade, America is under very serious threat from the "other," and that unless things change, we will lose what is fundamentally American.

Trump took that call up a level on Monday morning, with two tweets that aimed to not only draw a very bright line between "us" and "them" but also to raise the stakes of that made-up fight.

"Mexico has the absolute power not to let these large 'Caravans' of people enter their country. They must stop them at their Northern Border, which they can do because their border laws work, not allow them to pass through into our country, which has no effective border laws. Congress must immediately pass Border Legislation, use Nuclear Option if necessary, to stop the massive inflow of Drugs and People. Border Patrol Agents (and ICE) are GREAT, but the weak Dem laws don't allow them to do their job. Act now Congress, our country is being stolen!"

Let's parse what Trump is saying and doing here.

First off, the "caravans" mentioned here by Trump refer to, presumably, t he group of more than 1,000 people currently making their way through Mexico on their way to the US where they are seeking asylum . It's the fifth time that the group People Without Borders has led such a caravan of people -- who say they are fleeing persecution in their own countries. In 2017, there were two so-called caravans of 200 or so people; of that group, three have been granted asylum in the US while the others' fates are still being litigated.

So, unlike some (many?) of the things Trump tweets, there's truth here. But, what Trump is doing here has very little to do with the actual reality of these asylum seekers. After all, it's a relatively small group. And it's not the first time this has happened.

What Trump is doing is using the caravan to play on the fears of the country -- and, in particular, his supporters. The mental image he is conjuring is something out of " Mad Max Beyond Thunderdome ": Hordes of ill-intentioned people surging toward the US with malice in their minds.

They want to take what's ours, Trump is basically screaming. And they will if we don't stop them!

Whether or not Trump actually believes this (and I'm not sure he does), he absolutely knows what he is doing with this sort of language. This is the same sentiment that animates the "Make America Great Again" slogan of Trump's campaign and rhetoric like this from his inauguration speech : "Crime and gangs and drugs that have stolen too many lives and robbed our country of so much unrealized potential. This American carnage stops right here and stops right now."

The surface-level message of all of that goes like this: This country was made great by people like you and I. We shared a value system. We built all that you love about the country. But, these people don't think like us. They won't make America great. And I am the one willing to stand up for you and our values.

The just-below-the-surface message is this: White people made this country great. Brown people are flooding in. They pose an existential threat to your daily life and what the future holds for your children. If you don't fight back now, you may lose everything.

Another example of this came in January, when Trump spoke of countries from which he'd like to see more immigration. He mentioned predominantly-white Norway and not "shithole countries" like those in Africa. The comments blew up a bipartisan effort to pass legislation to give special legal status to people in the DACA program.

Appeals like these -- raw, emotional and designed to be a punch in the gut -- work in politics. Hope and change may be powerful motivators but they are nothing compared to fear and anxiety. Trump's 2016 campaign is a testament to just how powerful making people scared can be. Despite large majorities of people believing he was not temperamentally suited to be President and lacked the qualifications for the job , they voted for him anyway -- believing that we are under threat and that only Trump properly understood it.

As Trump feels more and more free to act in ways consistent with his gut -- and as Republicans continue to fret about the gap in base enthusiasm between their side and Democrats heading into the midterms this November -- all of this seems purposeful. There's no question that talk of invading hordes of immigrants rallies the Trump base. Ditto calls for the need for a wall.

"DACA is dead because the Democrats didn't care or act, and now everyone wants to get onto the DACA bandwagon," tweeted Trump on Monday . "No longer works. Must build Wall and secure our borders with proper Border legislation. Democrats want No Borders, hence drugs and crime!"

Trump knows what he is doing here. Look for a relentless focus on the wall and the threats posed by allegedly unfettered immigration between now and November. And it will likely gin up the GOP base.

That won't mean Republicans can dodge the likely hit they will take. But, it might mitigate it slightly.

But that doesn't make what he's doing presidential. Or right.