On Saturday night, St. Cloud police found 22-year-old Hallie Tobler dead with stabbing wounds.
St. Cloud police say they believe Tobler's husband was responsible for her death.
He was taken into custody with self-inflicted wounds. It was not clear if he had been officially charged with her murder.
Minnesota GOP Chair Alex Plechash said he spoke with Johnson shortly after the death of his daughter.
"My heart goes out to him and his family. Especially in the circumstances that we're discovering," Plechash said.
Johnson served on the St. Cloud city council from 2010 through 2018.
This year, he launched a longshot bid to seek the GOP nomination for governor. He finished eighth in an informal straw poll of voters last week.
You can contact the National Domestic Violence Hotline at 800-799-SAFE (7233) or text "START" to 88788 | thehotline.org