All 3 Uses of

republic
in
Arrowsmith

He was permitted, without restriction, to speak of himself as immoral, agnostic and socialistic, so long as it was universally known that he remained pure, Presbyterian, and Republican.
Chpt 2

Just between ourselves, and I don't want this to go any farther, I've been making some pretty good affiliations lately— been meeting some of the rising young Republican politicians.
Chpt 9 *

It was set to the tune of "The Battle Hymn of the Republic," but as the twins' voices were energetic and extraordinarily shrill, it had an effect all its own: Oh, are you out for happiness or are you out for pelf?†
Chpt 19

Definitions:

(1) (republic as in: the country is a republic)
of a system of government in which a majority of citizens elect representatives to make laws; or someone in favor of such a form of government
(2) (meaning too common or rare to warrant focus)
meaning too common or too rare to warrant focus:

As a proper noun, the word form Republican is commonly used to describe one of the major U.S. political parties. It is and has been used by many other organizations such as The Irish Republican Army.