US Senator Ron Johnson is sponsoring a “unity pledge” for the Republican candidates competing to take on US Senator Tammy Baldwin, requiring the Republican candidates to agree to support the eventual party nominee. Both state Sen. Leah Vukmir and Kevin Nicholson have said they will sign the pledge.

While the unity pledge has been in the works since December, Johnson’s statement about the unity pledge would seem more in response to recent involvement by national groups, including the national Club for Growth, in the Wisconsin campaign. Both the Vukmir and the Nicholson campaigns have received endorsements from national groups, and both candidates are backed by “Super PACs” funded by billionaires that make political expenditures independent of the two candidates’ campaign committees.

“We’ve all witnessed what happens when Washington, D.C.-based ‘political experts’ of all kinds get involved in U.S. Senate races,” Johnson said. “Here in Wisconsin, the grassroots have a track record of nominating candidates who reflect our values – not Washington’s – and we can do it again to defeat Tammy Baldwin this fall.”

In 2010, Johnson received the endorsement of the Republican Party of Wisconsin state convention and secured the party’s nomination in September despite no previous political campaign experience. He related that experience to the current race.

“The decisive ingredient in my two Senate race victories was our strong Wisconsin Republican Party grassroots structure in communities all across the state,” Johnson said. “I know firsthand what happens when you are able to earn the trust of the grassroots party faithful at the Republican state convention – you can receive their crucial endorsement.”

“That’s why, in my role as Chairman of the Grassroots Endorsement Process, I am calling on all Republicans who run for U.S. Senate in 2018 to pledge their support of our grassroots endorsement process and the eventual nominee in August,” Johnson said. “Wisconsin needs a person of integrity supported by the good folks of our state to help advance conservative reform and take on Washington’s professional political class. That person will need Wisconsin’s conservative grassroots to win.”

As the chairman of the Grassroots Endorsement Process, Johnson will be presiding over the vote at the party’s state convention which could possibly result in the party endorsing a candidate for senate prior to Republican primary in August. Candidates that sign the pledge will be given access to a list of the delegates to the GOP state convention which the candidates can use to woo support in hopes of getting the state party’s endorsement.

“All candidates running will be asked to sign a pledge to conduct a campaign focused on defeating Senator Baldwin and displaying mutual respect for their Republican competitors,” according to the Republican Party press release. “They will also be asked to acknowledge the existing rules and rules process for convention and agree to pursue the grassroots endorsement at state convention in a manner compliant with that process, and to support the eventual Republican nominee after the Republican primary in August.”

The unity pledge of support only applies to supporting the party’s nominee after the August Republican Primary, not if the convention endorses a candidate. The pledge does not affect or address the involvement of outside groups in the campaign. It only addresses the conduct of the candidates that sign the pledge.

Vukmir said that she would be proud to sign the pledge.

“As a lifelong Republican, I’ve always supported the party nominee and you can bet I’ll be doing everything I can this November to make sure Wisconsin has a Senator who believes in the Wisconsin Way,” Vukmir said in a statement released Wednesday. “Senator Johnson certainly understands that the grassroots are the core of Wisconsin’s Republican Party, a focus I have built my candidacy on.”

Nicholson’s campaign has also indicated it would sign the pledge. “Kevin of course will sign the unity pledge and he hopes that all Republicans will unite behind our nominee to defeat Baldwin,” said Nicholson spokesman Brandon Moody in a statement.

In addition to Vukmir and Nicholson, businessman Eric Hovde is also considering a run. Hovde ran in the Republican primary for US Senate in 2012 and finished second behind former Governor Tommy Thompson.

The 2012 GOP primary was especially divisive and even included a failed effort by former Congressman Mark Neumann to fill the convention with delegates friendly to his candidacy. To receive the party’s endorsement, the candidate must receive the support of 60 percent of the delegates at the state convention within three ballot attempts.