That's one of the biggest problems with the two party system. People say "I'm a conservative" or "I'm a liberal" and rarely vote based upon the issues.
Well, sorta. People tend to identify their party affiliation because it contains more of the prefferential stances on 'the issues'.
This is the standard unless people are allowed to directly vote on the issues rather than on a placeholder for them.
The issues also change so rapidly that someone who identifies as one party one year would find themselves identified by a completely different party ten years later.
That's why we have so many Reagon Republican zombies, even though by today's right wing standards, Reagon was a California liberal hippie.