Sen. Ron Johnson, junior senator from Wisconsin, endorsed Mitt Romney for president on NBC's Meet the Press on Sunday.
Johnson said that he had spoken with Romney on the phone and came away from those conversations convinced that Romney is the best candidate "to lead our party, to lead our nation."
"[Romney] is ready, willing and able to lead this nation," he said on Sunday. According to Roll Call, Johnson is the 19th senator and 94th Republican in Congress to endorse Romney this cycle.
Wisconsin's Tuesday primary is an increasingly important state for Romney to win, to gain both delegates and momentum.