Vice President Kamala Harris has selected Minnesota Gov. Tim Walz as her running mate, according to several sources close to the process, CNN first reported. 

Walz was one of three candidates shortlisted to be Harris' vice presidential candidate. The list also included Pennsylvania Gov. Josh Shapiro and Arizona Sen. Mark Kelly.

Harris and Walz will appear together at a Philadelphia rally Tuesday night, followed by appearances this week in battleground states such as Michigan and Wisconsin. An official announcement is expected in the coming hours, the Associated Press reported.

This is a developing story. Check back for updates.