That's like asking, "Why can’t repubs turn out a good chicken to watch the fox house?" No way does a genuine Republican ever win (or want to win) a race to become mayor of a concentrated Democrat parasite nest ("city"). Those places are strictly Democrat, and they can have 'em.
Ok, that’s a stupid statement. San Diego has been consistently run by Republicans for I don’t know how long and Montgomery, which is majority black, elected an active Republican to replace Bobby Bright when he went to Congress.
I also seem to recall that a Republican Jew was once able to become Mayor of a city that had a large black and Muslim population, I think it was Jersey City.
You know, in my state, Alabama, it’s the people in the cities who are Republicans while all the country folks remain “good ole’ Blue Dog Democrats.” The reason there even is a Democratic Party in this state is cause of rural people. It’s us city people who keep the Republican Party alive here.
Yes, it does seem that having a (D) in front of your name is a prerequisite for getting elected as mayor in Houston.
And the city council folks look like refugees from a traveling carnival.