It is rare that politicians ever understand when and where to
use music. They are forever using it when they don't have
permission or talking about it to show that they have a 'real
life' outside of politics, that they are just like us
really.
What they never seem to understand is that such use of music
does more harm than good. Instead of giving them a 'halo
effect', helping them to gain credibility and hopefully votes,
the potential backlash can be extremely embarrassing especially if
it keeps happening. In the worst case scenario it can also land
them with a hefty legal bill as well.
What usually happens is that they use music without the
artist's permission. However, the legal situation is very
complex.