Ironically, this will probably HELP them. It will allow them to appoint Ellison, the wacky progressive Muslim, to the senate where he won't have to stand up for reelection until 2020. If he went head to head with a GOP opponent in an open election, he would most probably lose, but with incumbency of a few years, he will have amassed a significant war chest and voting block.
Also, this allows the Dems to now go full throttle on getting Dough Jones elected in Alabama, which is frankly their main objective to throw a bunch of dems and Hollywood celebs under the bus, all for a shot of 2018.