The Pence team has recently asked senior Republicans for updates on Haley’s outreach to donors. And with Haley embarking on a national fundraising tour and promoting a new outside political group, top Pence advisers blame her for persistent rumors that she will replace him on the Trump’s ticket in 2020. Tensions flared after Haley chose not to publicly repudiate a Wall Street Journal column in June urging Trump to put her on the ticket.

Earlier this month, Haley took a swipe at Trump after his criticism of Baltimore and its black congressman, Elijah Cummings. “This is so unnecessary,” she wrote on Twitter, adding the eyeroll emoji. White House counselor and former Pence pollster Kellyanne Conway then fired back: “THIS is so unnecessary. Trump-PENCE2020,” Conway wrote of Haley’s tweet.

The shadow fight shows no sign of abating. Pence has spent the year barnstorming swing states that will determine the outcome of the 2020 election. But on Monday, he will head to Haley’s home turf of South Carolina to give the keynote speech at an annual barbecue hosted by GOP Rep. Jeff Duncan that has previously attracted White House aspirants. South Carolina is a gimme for Trump in the 2020 general election, but it will be key to anyone seeking a future Republican presidential nomination.