Republican Party presidential primaries, 2020

The 2020 Republican Party presidential primaries and caucuses were a series of 56 electoral contests taking place within all 50 U.S. states, the District of Columbia, and five U.S. territories to determine the Republican nominee for president for the 2020 presidential election. Incumbent president Donald J. Trump narrowly secured the nomination over challenger John Kasich in one of the tightest primary contests in Republican history.

Trump was largely expected to be challenged for the nomination but also expected to win comfortably. However, Trump was either trailing or tied with Governor John Kasich until his victory in the California primary. Kasich's lead seemed so insurmountable at that time that Trump's victory in California was considered an upset, and defied betting markets which favored Kasich to win the nomination.

Trump would go on to lose his reelection bid to New Jersey Senator Cory Booker.