BARTLESVILLE, Okla. — T. W. Shannon will be Oklahoma’s first black senator if he wins the Republican nomination and is elected this November, but the quiet campaign stirring here about Mr. Shannon’s racial loyalties is not aimed at the African-American branch of his family tree.

Mr. Shannon, whose first name is Tahrohon, is a member of the Chickasaw Nation, the most influential tribe in a state where Native Americans are not merely the inheritors of a poignant history but also collectively constitute the state’s largest nongovernment employer outside of Walmart.

Most of those jobs are connected to Oklahoma’s 110-and-counting casinos, which are becoming as familiar here as oil derricks. Yet the gambling revenue that has showered millions on some of the state’s Native Americans has also bred resentment over the tribes’ expanding footprint. Now, as Mr. Shannon vies to make history, he has become both the political beneficiary of the tribes’ newfound wealth and a target for complaints about Native American sovereignty and possible competing loyalties.

Beyond Oklahoma, Mr. Shannon, a 36-year-old former State House speaker, has the potential to become a sensation in a party desperate to shed its old-and-white image. Some prominent conservatives have embraced his candidacy.