Former Vice President Mike Pence publicly backed Karrin Taylor Robson in Arizona's Republican gubernatorial primary on Monday, going against former President Trump's endorsement.

Why it matters: Pence's endorsement underscores the growing divide within the GOP between the establishment wing of the party and the former president, AP reports.

Driving the news: Pence is expected to campaign with Robson, a housing developer, on Friday — the same day that Trump is set to hold a rally for former TV news anchor Kari Lake.

• The winner of the Aug. 2 Republican primary will likely become the state's next governor, Axios' Jessica Boehm reports.
• Pence said Robson is "the only candidate for governor that will keep Arizona’s border secure and streets safe, empower parents and create great schools and promote conservative values."

The big picture: Pence's endorsement also underscores the split between GOP lawmakers and candidates who have embraced Trump's false claims about the 2020 election and those who want to distance themselves from that rhetoric.

• Lake has aggressively promoted the false allegations that the 2020 election was rigged against Trump.

State of play: Arizona's gubernatorial primary is another test for Trump's endorsements — and his dominance over the GOP.

• Pence and other prominent Republicans backed Georgia Gov. Brian Kemp, who became a top Trump target after he refused to help him overturn the 2020 election results.
• Kemp won in a landslide in Georgia and fended off a Republican primary challenge from Trump-backed former Sen. David Perdue.

Go deeper... Trump endorsement tracker: Which candidates have won and lost