Gerry at Daly Thoughts posted an analysis on the percentage of circuit court nominations confirmed by the Senate.
A reasonable interpretation on that chart is that, starting with Reagan, the process began to become politicized. The Democrats became even more aggressive at this during George H.W. Bush’s term. The Republicans then upped the ante a bit under Clinton, particularly with his late second-term nominations. And under George W. Bush, the Democrats have decided raise the ante yet again.
It is even more stark if one looks at just the numbers for a President’s first Congress:
I recommend that you read the entire post and the comments.