GOP presidential front-runner Mitt Romney has picked up another endorsement from a Wisconsin Republican ahead of the state's primary Tuesday.
Johnson tells NBC's "Meet the Press" that Romney is "ready, willing and able to lead this nation'.'
The senator isn't saying the other Republican candidates should drop out. But Johnson says Romney is the only candidate with a realistic chance of getting the necessary number of delegates to win the nomination.
Johnson also says the candidates have had "a spirited debate" but he thinks it's time "to end this" and prepare for the campaign against Obama.
On Friday, Wisconsin Rep. Paul Ryan, chairman of the House Budget Committee, endorsed Romney.