Why do theme attributes take precedence over spinner attributes?

Question

Android

Theme attribute

<item name="android:background">@color/white</item>

does not allow my spinner attribute to work

android:popupBackground="@drawable/spinner_pop_up_background

Which is strange because android:popupBackground is supposed to have a higher priority. If the attribute is commented out in the theme, the spinner is drawn correctly, but the fragment animations begin to work incorrectly when the back button is pressed. Fragments that leave have a transparent background. Why does the theme override View attributes? I tried to take out android:popupBackground in a separate theme and specified it in theme for Spinner. Did not help.