MADISON, Wis. (CBS 58/AP) — Republican U.S. Sen. Ron Johnson of Wisconsin, one of former President Donald Trump's most vocal supporters, says he will seek reelection to a third term.

Johnson announced his decision Sunday. When Johnson ran for reelection in 2016 he vowed to only served two terms, but said things have changed since Democrats control both houses and the White House.

“So today, I am announcing I will continue to fight for freedom in the public realm by running for re-election," Johnson said in a statement. 

The Oshkosh Republican, first elected in 2010, has been one of former President Donald Trump's vocal supporters. Trump endorsed and encourage him to run in April.

Over the last year, Johnson has made numerous headlines for his controversial comments regarding COVID-19 vaccines and downplaying the Jan. 6 attack.

He's questioned the effectiveness of vaccines, criticized top health experts for overhyping the coronavirus pandemic and denied climate change.

Johnson has faced backlash about his comments from his Democratic opponents seeking to unseat him.

The Senate race will likely be one of the most hotly contested in the country given that President Joe Biden won Wisconsin by fewer than 21,000 votes after Trump's similarly narrow victory in 2016.

"We're going to be seeing a ton of of interest nationally," explained Mordecai Lee, political expert and professor emeritus at UW-Milwaukee. "Of all the races for the U.S. Senate in November, this one will probably be the one that's the most purple. In other words, it could just as easily go Democratic and just as easily go Republican."

Lt. Governor Mandela Barnes, state Treasurer Sarah Godlewski, Milwaukee Bucks executive Alex Lasry and Outagamie County Executive Tom Nelson are some of the top Democratic candidates in the U.S. Senate race.

Others include, radiologist Gillian Battino, Milwaukee Common Council member Chantia Lewis and Peter Peckarsky, a Milwaukee attorney.

"I think once there's a Democratic nominee and it's down to one-on-one, this is going to be like an old cowboy movie," Lee predicted. "A shootout on Main Street. I'll make a prediction that we're going to see the highest spending for a U.S. Senate race Wisconsin has ever seen."

The Democratic Party of Wisconsin released the following statement:

“Ron Johnson has been in the Senate looking out for himself at the expense of Wisconsinites and failing to do the job he was elected to do, and it’s time to face the consequences. Whether he was manipulating the GOP tax scam bill to enrich himself and his biggest political donors, trying drive up health care costs and rip away protections for pre-existing conditions, or failing to crack down on China’s illicit economic practices and companies that outsource our jobs, Johnson has proven over and over again he’s only ever focused on serving himself. In 2022, Wisconsinites will hold Ron Johnson accountable and elect another Democratic senator who will put the interests of our state’s working families first.”