No true Scotsman
Another argument that is a fallacy is "Darcy is not really a Democrat because she is against abortion." Even though most Democrats are for some levels of abortion, not all people who vote for Democrats are for abortion. Darcy might agree with the Democratic Party on other issues, like having a higher minimum wage or spending less money on the military, but disagreeing on one issue does not automatically make her not a Democrat. In fact, most people who vote for certain political parties will not agree with their party on every issue, but they will agree on the issues that are most important to themselves.