Julia Letlow

The Republican Senate primary in Louisiana has narrowed to two candidates after the incumbent, Bill Cassidy, who voted to convict Donald J. Trump in his impeachment trial five years ago, was defeated on Saturday.

The two top vote-getters, Representative Julia Letlow and State Treasurer John C. Fleming, are headed to a runoff scheduled for June 27. The winner will be heavily favored in the general election because of the state’s strong conservative tilt.

Neither candidate secured the majority of the vote needed to advance to the November general election under Louisiana’s system. Ms. Letlow won about 45 percent of the vote, and Mr. Fleming finished with around 28 percent. (Senator Cassidy picked up roughly 25 percent.)

Here’s what to know about Ms. Letlow, 45, and Mr. Fleming, 74.

Mr. Trump endorsed Ms. Letlow.

The congresswoman, a former teacher and university administrator from Monroe, was backed by the president even before she formally entered the race. In January, Mr. Trump urged Ms. Letlow to challenge Mr. Cassidy, writing on social media: “RUN JULIA RUN!!!”

After she finished first on Saturday, the president celebrated not only Mr. Cassidy’s loss but Ms. Letlow’s step toward the Senate.

“Julia Letlow is a spectacular person, and will never let you down!” Mr. Trump wrote on social media.

She first ran for Congress after her husband, a representative-elect, died of Covid-19 complications.

Ms. Letlow, the first Republican woman elected to Congress from Louisiana, first won her seat in early 2021. She emerged from a special election to claim the seat her husband, Luke Letlow, won the previous November; he died the following month of complications from Covid, days before he was to take office.

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