Transcript for Trump orders more than 5,000 troops to US-Mexico border

As the president heads to Pittsburgh with one week to go before the midterms he's putting the focus on immigration with a new plan to send more than 5,000 troops to the u.s./mexico border opponents are calling a political ploy and this is the largest in decades. Is it justified by an actual threat? Reporter: Well, George, first of all, this is a significant deployment of active duty U.S. Military. To put it in context it's twice the number of troops that are currently deployed in Syria and if you look at the situation, it sure looks more like a political move tied to the midterm elections than an actual effort to control the border. For one thing, consider the fact that this caravan that the president talks about is still some 900 miles from the border and these troops cannot actually control the border. By law all they can do is support the border patrol. They cannot take part in law enforcement. They can only do things like transporting border agents or building tents and finally, this is a temporary deployment. This is 45 days' deployment and by some estimates this caravan won't even reach the border for another 45 day. We are one week from the election and a new report that the president is considering an executive order to do away with the so-called birthright citizenship that anyone born in the United States is a citizen even if their parents are not. A lot of constitutional experts says the president can't do that. Reporter: The supreme court has never directly ruled on this question of whether or not somebody born to undocumented immigrants would be a citizen but that's been the interpretation in the 14th amendment and the president, one thing is certain, cannot change the constitution with an executive order. And, Jon, we've seen a series of tweets from the president yesterday continuing this strategy of delegitimizing the media calling them the enemy of the people and blaming the media for a lot of problems we're seeing over the past week. You had a pretty contend shoes exchange yesterday. Why is he out there attacking -- The first thing he did was condemn the attacks, both in Pittsburgh and in the pipe bombs. The very first thing the media did was blame the president and make him responsible for these ridiculous acts. Why is the president suggesting it's the news media? The president is the one placing blame here. No, the president isn't placing blame. He is not responsible for these acts. Reporter: It's a jarring line of attack, George. The president on one hand you hear it from Sarah Sanders talk about peace and harmony and uniting the country and then littering blaming the, quote, fake news media for the level of hate in the country. But it's a classic trump tactic. If you go back to 2016, Lesley Stahl asked him why he does it and according to Lesley Stahl the president responded back then, you know why I do it, I do it to discredit you and demean you all so when you write negative stories about me, nobody will believe you. Jon Karl, thanks very much.

This transcript has been automatically generated and may not be 100% accurate.