Republican presidents since Reagan have understood the importance of the judicial nomination process in transforming the federal judiciary to their political purposes. By successfully pushing young, extremely conservative nominees, Reagan and the two Presidents Bush have been able to completely reshape not just the Supreme Court, but the lower federal courts throughout the country. When Clinton was president, the courts were simply not a priority. Rather than extend his precious, if mythical, political capital, he sought to avoid bruising confirmation battles by appointing mostly moderates and not putting up a fight when Republicans challenged more liberal nominees. Obama, like Clinton, has been far less aggressive than his Republican predecessors in pushing for judicial appointments.
The Democrats initially used the filibuster effectively to thwart some of George W. Bush's more extreme judicial appointments. But then they blinked. In 2005, Republicans threatened to employ the so-called nuclear option, which would have changed the Senate rules to preclude filibusters for judicial nominees. Seven Democrats joined seven Republicans to form the "Gang of Fourteen," and signed an agreement in which the Republicans in the gang would not vote for the nuclear option and the Democrats would not filibuster except in extraordinary circumstances.
In practical terms, this meant that Bush was able appoint the conservatives he wanted to the bench and the Democratic minority, without the seven members of the gang, could not stop him. Thus, five nominees who had originally been filibustered, and several other conservatives, became federal judges, and, perhaps most significantly, Samuel Alito's nomination to the Supreme Court was permitted an up-or-down vote. He was confirmed by a vote of 58-42, with enough Senators voting against him to have successfully filibustered and prevented a vote on his confirmation.
Which brings us to the Obama administration. Last term, the Republicans, in stark contrast to Democrats during the Bush administration, effectively stalled votes and used the threat of filibuster to thwart a record number of nominations. Compounding this failure was President Obama's inexplicable refusal to make a concerted push for his worthy and mostly non-controversial nominees. This term appears to be little better.