Michael Watson defeated Sam Britton on Tuesday in the Republican primary for secretary of state, a race that featured the most mudslinging of the statewide primaries.

Watson, a state senator from Pascagoula, focused his campaign messaging on highlighting the fact that Britton ran for the state House of Representatives as a Democrat in 2003 and donated to the campaigns of former Democratic Gov. Ronnie Musgrove in 2003 and 2008.

Britton, a public service commissioner from Laurel, hit Watson in several ads and political appearances that focused on Watson’s donations to a political action committee that worked to keep Donald Trump from receiving the Republican nomination in 2016.

Britton used social media to thank his supporters.

“I want to thank all of you for your gracious support of Robin and me these last several months. I called Michael Watson a moment ago to congratulate him on his victory and to wish him well and offer my full support in the General Election,” he said on Twitter late Tuesday.

The secretary of state serves as the state’s elections chief, overseeing voting in Mississippi, which until recently was required to seek federal Justice Department approval for changes to voting laws because of the state’s history of racial discrimination in its election laws.

Watson faced scrutiny during the primary campaign for his role in the 2014 election challenge from state Sen. Chris McDaniel, who nearly defeated U.S. Sen. Thad Cochran in a Republican primary runoff. McDaniel never conceded the race, and Watson joined McDaniel’s legal team in challenging the results of the primary in state courts.

Watson served on McDaniel’s legal team, which sought to invalidate what they called “illegal and fraudulent” African American votes in the runoff, arguing that blacks voting in the Republican primary cost state Sen. Chris McDaniel the election.

Watson deflected attention this year from his role in the 2014 election challenging, saying he is the only Republican primary candidate “who understands the law and duties of the (secretary of state) office.”

During his campaign this year, Watson has focused his policy pitches on keeping “illegal immigrants off our voting rolls,” strengthening the state’s cyber security systems to “make sure our elections are protected,” and addressing problems with long waits at the state’s driver’s license bureaus.

Watson has also pitched moving the state’s drivers license bureaus from the Department of Public Safety to the Secretary of State’s office.

Watson will face Johnny DuPree, who won the 2011 Democratic nomination for governor, in the November general election. DuPree, the 16-year mayor of Hattiesburg, handily defeated Maryra Hodges Hunt in the Democratic primary on Tuesday.