U.S. Sen. Ron Johnson slammed Hillary Clinton during his speech to Republicans gathered in Milwaukee for their annual convention.
The Oshkosh Republican said he had "kept those promises" he made to voters when he ran for Senate, like his vow to oppose "Obamacare."
But he accused former Secretary of State Hillary Clinton and President Barack Obama of lying to the American people.
He said Clinton, likely Democratic nominee for president in 2016, lied about the tragedy in Benghazi to "cover up her dereliction of duty."
The Republican crowd booed at the mention of Clinton's name
"The American people deserve to be told the truth," Johnson said.
"The Democrats, the liberals, the progressives, they’re relentless in their denial of our freedoms," he added. "If we’re united, we can win, we can save this nation."
Democrats quickly responded, saying that Johnson is an embarrassment to the state of Wisconsin.
"After nearly four years on the job, Ron Johnson's greatest accomplishment is attracting negative, embarrassing headlines for Wisconsin," said Mike Tate, chairman of the Democratic Party of Wisconsin. "Wisconsin voters will run, not walk, to the polls in 2016 to elect a new senator."