(CNN) Florida Sen. Bill Nelson compared the current political climate in the United States to that of the African country of Rwanda before a genocide that killed about 800,000 people in the 1990s.

Nelson, a Democrat who is facing a stiff re-election challenge from Florida's current Republican governor, Rick Scott, made the comment Sunday while stumping at the Covenant Missionary Baptist Church in Florida City, Florida. Nelson was accompanied at the event by Democratic California Sen. Kamala Harris.

Nelson described his wife's relationship with Rwanda's current first lady, Jeannette Kagame, and said tribalism is sweeping through US politics to a dangerous degree. He called the story of the Rwandan genocide "instructive" to Americans.

"When a place gets so tribal that the two tribes won't have anything to do with each other ... that jealousy turns into hate," Nelson said. "And we saw what happened to the Hutus and the Tutsis in Rwanda, it turned into a genocide. A million-people hacked to death within a few months. And we have got to watch what's happening here."

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