The signal sent

Arpaio and Trump

What Trump's pardon of Arpaio means:

The President just showed the world, and more importantly those who may be considering testifying or providing evidence against him, that if they remain loyal to him, he will remain loyal to them. Paul Manafort, Michael Flynn, Carter Page, and just about everyone else who may have incriminating evidence related to Mueller’s investigation into possible Trump campaign collusion, just got the signal that if they don’t cooperate with the government a Presidential pardon seems quite likely. Basically this was Trump’s way of obstructing justice without actually breaking the law.