Well they did do it in New Jersey with lautenberg when their senatorial candidate earned a well-deserved federal vacation...
It isn't fair that the dems do not have a candidate, so put Lautenberg in to replace him.
Actually I suspect Obama will attempt to "delay" the election for a year so the Dems can select a candidate. In the mean time Obama will get an extension to his reign
The Democrat who best checks all of these boxes is Senator Kristin Gillibrand of New York. If the Democrats substitute Gillibrand some time after Labor Day, there will be no stopping her, and she will be the next President of the United States.