It means the Democrats can block Trump because his party is no longer in power. It also means nothing will get done for the next two years as Trump can veto any Democratic led legislation. As for the supreme Court, the Senate can block any of Trump’s nominees. For the presidential election there is no impact. The US voter has a short memory and the Democrats will be blamed for not getting anything done over 2 years even if it was Trump blocking everything. The Republican voter will come out in force and undo some of what happened last night. The Democratic Party needs to remember that this wasn’t a vote for them but a vote against Trump