A mandate is only a mandate

if it is what you voted for and what you believe in.  This is the way politics works. Yes? I put that to a certain professor of politics yesterday.  And no, of course I am not being completely serious about it.
But there is an element of truth in it. 
I haven't read the article the professor wrote on Trump's "Border Wall" but he has apparently written a piece in which he states that, for Donald Trump his border wall was mandated by the voters.
And yes, perhaps it was. People went out and voted for him. He became President - something I don't believe he really expected to happen - and then he had an election promise to keep. He had said he would build a wall - and that Mexico would pay for it.Now he is saying America will pay for it. The government has had to shut down because he refuses to  back down. Voting is not compulsory there and a minority of those eligible to vote bothered to vote.
Does he have a mandate or not?
In the UK the Brexit deal has been limping along and, at present, it looks as if there will be no deal. The Prime Minister there has said she has obtained the best possible deal and that MPs should just accept  that nothing better is going to happen. She claims she is acting on what the people voted for.  Voting is not compulsory there and not everyone voted.
Does she have a mandate or not?
In this country it is compulsory to "attend the ballot box" and most people vote as a consequence. (It is not actually compulsory to vote.) The present parliament has not been able to get any number of pieces of legislation through parliament because the legislation has been blocked in the Senate where the Opposition and the cross bench/independents have the numbers. 
Does the government here have a mandate or not?
I once had the rather odd task of clearing out the filing cabinets of a former politician. There were thousands of documents there. Many of them dealt with legislation the politician had worked on both in government and in opposition. The opposition pieces were often marked, "pass with reservations". It meant that, in opposition, the party would argue it in parliament but still allow the legislation to go through. 
That was a long time ago now and things seem to have changed. There seems to be a determination to deny democracy. I don't think walls are the answer (but I do know there can't be an unrestricted flow of migrants). I don't think Brexit is the answer (but I do think the EU needs to undergo some drastic changes). I have seen good legislation fail to pass here simply because the Opposition has seen the opportunity to ensure the government fails - and fails again. I know there are plans to introduce almost identical legislation into parliament when the new government comes in. It is not about what is best for the country but about attaining and retaining power.
There seems to be a determination to deny democracy. That "mandate" only applies to those things we believe in and support. It has nothing to do with what the majority wanted.