It should be harder to get party membership Democratic or Republican or Other

It should be harder to get party membership Democratic or Republican or Other.  Anyone can have a party membership without screening.  To join a party, a person should at least agree with most of the party’s positions on issues and policies.   A person will never agree with all such positions on issues and policies, but the GOP membership right now is mostly [it seems] not conservative or near right/left of conservative.  Extreme right or left members should join a party more in line with their concepts and not destroy an existing party that is not extreme or radical.  Such extremists or radicals should not be allowed to infiltrate [evenly slowly over years] a party and destroy its basic stance on issues and policies or their methods.