Ex-US Vice President Mike Pence to launch 2024 election bid, challenging Trump

FILE PHOTO: Former U.S. Vice President Mike Pence addresses the National Review Institute's 2023 Ideas Summit in Washington, U.S., March 31, 2023. REUTERS/Kevin Lamarque/File Photo

(Reuters) - Former Vice President Mike Pence, who served Donald Trump with unwavering loyalty but later turned on him after the 2021 attack on the U.S. Capitol, will formally challenge his former boss for the Republican presidential nomination on Wednesday.

It is extremely rare for a vice president to run against a president he served under, and it has happened just a handful of times in U.S. history. Pence enters the Republican presidential primary with a mountain to climb, polling at just 5% and trailing Trump by 44 points, according to a Reuters/Ipsos opinion poll in May.