Ah, the whole purpose of a political convention is to tell people in your party who to vote for.
Wrong.
It is to establish a party platform and nominate candidates who espouse that platform.
In this country, no one 'tells' someone who to vote for.
When I lived in the UK, one voted a party, not anything else, and the party selected the candidates who would run for office. There was not even a geographic element to it.
That just is not the way it is done here.