There is no pending staff shakeup in the office of Sen. Ron Johnson (R-Wis.), his spokesman said late Thursday.

Sen. Ron Johnson (R-Wis.). (Win McNamee/GETTY IMAGES)

The report said Johnson’s decision and the turmoil it is causing have exasperated senior Republicans, who fault the senator for not diligently building relationships with his GOP colleagues and for isolating himself .

“This story is categorically untrue,” Johnson press secretary Brian Faughnan said late Thursday, adding that “the allegations come only from unnamed sources reporting second and third-hand rumors.”

The senator has had very little staff turnover and “is also proud of the relationships he has built with his Senate colleagues — which was shown pretty clearly when he garnered 22 votes in his recent Republican Senate leadership race,” Faughnan added in an e-mail. “You can’t do that without establishing relationships.”

Despite the denial, Roll Call noted that Johnson’s legislative director, Robert Duncan, has departed for new opportunities.

Founder of a plastics company, Johnson spent $4.4 million of his own money to unseat Sen. Russ Feingold (D-Wis.) in 2010. A businessman for his entire professional career, Johnson’s first foray into politics came at a tea party event in October 2010. He has emerged as a vocal conservative critic of President Obama’s policies and makes frequent television appearances — especially on Sunday morning political talk shows and cable business news channels — to tout GOP fiscal and economic policy.

But Johnson came up short in December in a bid against Sen. Roy Blunt (R-Mo.) to win the No. 5 spot in Senate GOP leadership, a race that some described as a proxy battle between establishment Republicans and younger, tea party-backed lawmakers. Despite the loss, some GOP activists want Mitt Romney to consider Johnson as a vice presidential running mate or as a potential member of his Cabinet.

Follow Ed O’Keefe on Twitter: @edatpost

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