Ron Johnson, G.O.P. Senator From Wisconsin, Will Seek Re-election

WASHINGTON — Senator Ron Johnson, a Republican from Wisconsin who over the last year has become the Senate’s leading purveyor of misinformation about elections and the coronavirus pandemic, announced Sunday that he would seek re-election to a third term.

Mr. Johnson, 66, had pledged to step aside after two terms but opened the door to a third shortly before the 2020 presidential election.

His entry into the race is certain to focus enormous attention on Wisconsin, a narrowly divided political battleground where Gov. Tony Evers, a Democrat, faces his own difficult re-election bid in a race that may determine control of the state’s election systems ahead of the 2024 presidential contest.

“Today, I am announcing I will continue to fight for freedom in the public realm by running for re-election,” Mr. Johnson wrote in an essay published Sunday in The Wall Street Journal.