No person shall be eligible to election as Resident Commissioner who is not a bona fide citizen of the United States and who is not more than twenty-five years of age, and who does not read and write the English language. In case of a vacancy in the office of Resident Commissioner by death, resignation, or otherwise, the governor, by and with the advice and consent of the senate, shall appoint a Resident Commissioner to fill the vacancy, who shall serve until the next general election and until his successor is elected and qualified.