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PEWAUKEE, Wis. - Freshman Wisconsin Sen. Ron Johnson endorsed Mitt Romney Sunday morning, adding to the growing list of key republicans who have thrown their support behind the candidate over the past week alone.

Johnson, who now joins the ranks of Romney endorsers from the past few days that include Florida Sen. Marco Rubio, former President H.W. Bush and Wisconsin Rep. Paul Ryan, said this morning on NBC's "Meet the Press" that he had never intended to make an endorsement but that Romney's private sector experience had convinced him to do so.

"I never did intend to endorse anybody but I've had the opportunity to meet with Governor Romney over the last couple weeks, have long phone conversations with him," said Johnson. "I've come away from those conversations fully convinced that Governor Romney is the person to lead our party, to lead our nation."

"He fully understands the gravity of our financial situation. He's dedicated toward solving those problems," said Johnson.. He is ready, willing and able to lead this nation, unlike President Obama. So today I'm happy to announce my full support and my endorsement of Governor Romney to be the next President of the United States."

Johnson, a longtime businessman who served as the CEO of a plastic manufacturer, emerged as a tea party favorite during the 2010 election, when he defeated three-term Sen. Russ Fiengold in the Wisconsin race.

In a written statement, Romney welcomed the endorsement, writing, "I look forward to working with Ron during the campaign to develop that agenda, and after the election, to reverse the disastrous policies of Barack Obama."