If it gets blocked, the reasoning will likely include that something of this magnitude will have to be approved by congress, which would prevent basically anything Biden/executive branch can do unilaterally. It's also going to turn this into an election issue for the next election and considering it massively affects around 40 million people from across the political spectrum, which doesn't bode well for republican party that is increasingly catering to their most extreme members and alienating the moderates and centrists they NEED to win even moderately contested races.