The first test for Kevin McCarthy’s revenge tour comes Tuesday in South Carolina, where GOP Rep. Nancy Mace is facing a primary challenger backed by the former House speaker.

Mace, one of the eight House Republicans who voted to oust McCarthy from his leadership post in October, has faced millions of dollars in ad spending from outside groups aligned with the former California congressman. McCarthy’s leadership PAC also donated to her main Republican opponent in the Charleston-based 1st District, attorney Catherine Templeton.

Still, Mace has outraised Templeton and has received support on the airwaves from the conservative Club for Growth Action. She also has an endorsement from former President Donald Trump.

Mace is looking to win a majority of the primary vote on Tuesday to avoid being forced into a runoff later this month. Marine veteran Bill Young will also be on the ballot along with Mace and Templeton.

In South Carolina’s 4th District, GOP Rep. William Timmons is also facing a hotly contested primary against state Rep. Adam Morgan, who chairs the Freedom Caucus in the Legislature. Morgan has support from some of Timmons’ hard-line House colleagues, turning the race into a proxy fight over internal divisions in the Republican conference. Trump endorsed Timmons in the primary.

In South Carolina’s open 3rd District, Trump has backed pastor Mark Burns in the GOP primary, which is expected to head to a runoff with multiple candidates on the ballot.

Outside of South Carolina, Nevada, North Dakota and Maine are also holding primary elections on Tuesday. And Trump has intervened in many of the key races.

Trump made a last-minute endorsement in Nevada’s GOP Senate primary, backing Army veteran Sam Brown over his former ambassador to Iceland, Jeff Gunter. The winner will face Democratic Sen. Jacky Rosen in the fall in what will be a critical race in the fight for Senate control.

Trump also put his thumb on the scale in Nevada’s 4th District, backing former North Las Vegas Mayor John Lee in the race to take on Democratic Rep. Steven Horsford.

In North Dakota, Trump has endorsed GOP Rep. Kelly Armstrong for governor. That put the former president on the opposite side of one of his potential running mates, retiring Gov. Doug Burgum, who backed Lt. Gov. Tammy Miller.

Trump also supported Public Service Commissioner over former state Rep. Rick Becker in the primary to replace Armstrong in North Dakota’s at-large district.

In Maine, the former president backed state Rep. Austin Theriault in the GOP primary in the 2nd District, where Rep. Jared Golden is one of five Democrats running for re-election in a district Trump carried in 2020.

Aside from Tuesday’s primary contests, voters in Ohio’s 6th District will pick a new member of Congress to replace former GOP Rep. Bill Johnson, who resigned in January. Republican state Sen. Michael Rulli is expected to win the deep-red seat, which would boost Republicans’ slim House majority.

Polls close at 7 p.m. ET in South Carolina, 7:30 p.m. ET in Ohio, 8 p.m. ET in Maine, 9 p.m. ET in North Dakota and 10 p.m. ET in Nevada.

This article was originally published on NBCNews.com