Didn't Mitch McConnell set the precedent for waiting until after the next election before considering a Supreme Court nominee to SCOTUS?
No, contrary to what other people have said about everybody doing it, the one and only time that the Senate refused to even consider a vote on a Supreme Court Nominee was due to Mitch McConnell refusal in 2016, to allow a vote.
Why do some Republicans think they can hold the White House hostage?
The Senate has passed legislation to freeze the Bush tax cuts for 98% of Americans and 97% of American small businesses. The President agreed today to sign it. Republicans also agree that all these people and businesses should have their tax rates frozen at Bush levels. No one is in disagreement. What happens if the tea party controlled House Republicans refuse and elect to use these tax cuts as a bargaining chip in the fiscal cliff debates? Nothing to the Democrats really. They offered the tax cuts, the House refused. Besides, Democrats like tax increases, particularly if they can blame them on Republicans. I don't see any way that Republicans can blame Democrats for costing 98% of Americans and 97% of America's small businesses billions upon billions in higher taxes.