Incumbent Democratic President Barack Obama was not eligible to serve a third term. Former Secretary of State Hillary Clinton was able to secure the Democratic nomination. Trump became his party's front-runner against many candidates in the Republican primary, defeating Senator Ted Cruz, Senator Marco Rubio, and Ohio Governor John Kasich among other candidates. Many third-party candidates ran, such as Gary Johnson. Trump chose Governor of Indiana Mike Pence as his running mate, and Clinton chose Senator Tim Kaine as her running mate. 