50. the answer is...

vote in a federal election
run for federal office

U.S. citizens have the right to vote in federal elections. Legal permanent residents can vote in local or state elections that do not require voters to be U.S. citizens. Only U.S. citizens can vote in federal elections. U.S. citizens can also run for federal office. Qualifications to run for the Senate or House of Representatives include being a U.S. citizen for a certain number of years. A candidate for Senate must be a U.S. citizen for at least 9 years. A candidate for the House must be a U.S. citizen for at least 7 years. To run for president of the United States, a candidate must be a native-born (not naturalized) citizen. In addition to the benefits of citizenship, U.S. citizens have certain responsibilities— to respect the law, stay informed on issues, participate in the democratic process, and pay their taxes.