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MADISON, Wis. — Republicans decided Tuesday to place only President Donald Trump's name on Wisconsin's presidential primary ballot this spring, making it a challenge for any long-shot GOP candidates to run against him in the state.

A committee made up of Republicans and Democrats met with state election officials in the state Capitol to decide which candidates will be listed on the April 7 primary ballot. The Republican committee members submitted only Trump's name, and he was approved on a unanimous voice vote.

The Democratic committee members submitted 14 candidates, including Joe Biden, Michael Bloomberg, Bernie Sanders, Amy Klobuchar and Elizabeth Warren. They were all approved on a unanimous voice vote, as well.

The Republican move freezes out any other GOP candidates, including former Massachusetts Gov. Bill Weld and former Rep. Joe Walsh of Illinois.

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Walsh tweeted after the committee vote that Republican Party bosses are trying “to protect their King. This isn't Russia. This isn't China. This kind of un-American (expletive) shouldn't happen here.”

No one immediately responded to an email sent to the Weld campaign's media inbox seeking comment.

Wisconsin Republican Party Chairman Andrew Hitt told reporters after the meeting that Weld and Walsh have failed to get on primary ballots in a number of other states, making them “less relevant” in Wisconsin. He added that the party hasn't seen any activity from either campaign in the state and didn't hear from either camp until Weld's people contacted the party on Monday.

“We haven't seen a commitment,” Hitt said. “They didn't do the work."

Hitt pointed out that they could still get on the ballot without the committee's approval. Under Wisconsin law, candidates who weren't selected can force their way on if they submit 8,000 nomination signatures by Jan. 28.

Trump's allies have been working for months to clear the primary field across the country for the president in the face of challenges from dark horse candidates.

The Minnesota GOP, for example, plans to list only Trump on its March 3 primary ballot. Republicans also have canceled primaries in a number of states, including South Carolina, Nevada, Arizona and Kansas, to clear the field for Trump and consolidate support.

Such moves aren’t unprecedented, but they aren't common. Republicans and Democrats canceled contests to protect their incumbents across up to 10 states in 1992, 1996, 2004 and 2012.