This post has been updated.

Wisconsin Republican Sen. Ron Johnson on Sunday endorsed Mitt Romney’s presidential bid, giving the former Massachusetts governor his latest boost from a congressional backer ahead of Tuesday’s Badger State primary.

Sen. Ron Johnson (R-Wisc.), center, endorsed Mitt Romney on Sunday. (T.J. Kirkpatrick/Getty Images)

“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 said in an appearance on NBC’s “Meet the Press.”

He cited Romney’s private-sector background as well as his “executive experience in government” during his tenure as governor of Massachusetts.

“I never did intend to endorse anybody, but I’ve had the opportunity to meet with Governor Romney over the last couple weeks, had long phone conversations with him,” Johnson said. “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. He is ready, willing and able to lead this nation, unlike President Obama.”

The move comes days after another top Wisconsin Republican, House Budget Committee Chairman Paul Ryan, endorsed Romney.

In a statement, Romney hailed Johnson's "life-long experience as a successful manufacturer and job creator."

"His understanding and focus on our debt and deficits, and pointed questioning of administration officials, has quickly gained Ron the respect of colleagues and the appreciation of hard working Americans," Romney said.

A tea-party favorite, Johnson is a businessman who had never served in office before running in 2010 against longtime incumbent Sen. Russ Feingold (D-Wis.).

Late last year, he ran against Sen. Roy Blunt (R-Mo.) for the No. 5 position in Senate Republican leadership in a proxy battle that pitted the tea party against the GOP establishment. Blunt ended up winning the race, although his 25 to 22 victory was a narrower one than many expected.

Johnson said Sunday that Senate Minority Leader Mitch McConnell (R-Ky.) has tapped him to head up a joint messaging effort between Republicans on Capitol Hill and the Romney campaign – a role that may be a nod by top Senate Republicans to Johnson’s strong performance in the leadership race.

“I've been asked by Leader McConnell to lead an effort, coordinate our agenda and our message in the House, the Senate, with the presidential candidate, so we can communicate to the voters of America the very clear choice in our approach,” Johnson said. “We actually want to rely on the private sector. We know it's freedom in the free market system versus president Obama's approach, growing government, growing government intrusion in our lives. I'm looking forward to making sure President Obama is a one-term president.”

Johnson’s endorsement of Romney gives the former Massachusetts governor the backing of a member of the Senate’s new guard, an up-and-coming freshman who is popular with tea-party supporters. Last month, Sen. Mike Lee (R-Utah), another tea-party-backed freshman, threw his support behind Romney.