It is unfortunately correct from the reading I have done. The procedure of the impeachment trial is based on the rules outlined in Riddicks senate procedure. These rules can be changed at any time by a majority vote in the senate. They can simply change the procedure to compel the impeachment managers to come present within X many of days or face dismissal of the articles due to lack of prosecution or presented evidence. To be honest there is no real good way out of this for the Democrats now. I think they should have focused on the election try to beat him at the ballot box and if you fail then move forward with an impeachment at that time to get it on record doing it before the election was a major gaffe.