Mont. Code Ann. § 5-5-420

If the objection to the sufficiency of the articles of impeachment is not sustained by a majority of the members of the senate, the defendant must be ordered to immediately answer the articles of impeachment. If the defendant pleads guilty, the senate shall render judgment of conviction against the defendant. If the defendant pleads not guilty or refuses to plead, the senate shall, at the time that it designates, proceed to try the impeachment.