Republicans doing it a bit more may just be a perceptual illusion because we just got done with 8 years of Obama where the GOP had an active strategy to minimize (what they felt was) the destruction his policies would entail. Ultimately, both parties do it to "obstruct" the other side from making progress, limit the damage inherent in the majority passing its policies, wield power and leverage over ongoing policy discussions, and most importantly, to whip up enthusiasm among their respective bases for maximum turn out during the mid terms. Its simply a byproduct of bifurcated gridlock where political parties are incentivized to not cooperate because it yields more power and interest formation within their respective camps.
I don't see any illusion. No President has ever gotten all his lower court judicial nominees through COngress. The system is designed for minority to have some ability to stop extreme nominations. This is designed to incentivize more moderate nominations.
So a President not getting all his judicial nominees does not equal obstructionism, that is simply the system working as intended.
This is night and day difference from the Senators from one party clearly breaking their Oath to uphold the Constitution solely to prevent a President from exercising his Constitutionally granted right to nominate a Supreme Court Justice. This is unprecedented level of breaking the public servant oath to the Constitution.
Its not an illusion. There is simply no comparable event from the modern Democratic party (FDR-current). The closest you get is what happened to Robert Bork, a far right Reagan nominee that the Democrats blocked. But, and this is a pretty massive BUT the difference is the Democrats did let Reagan get his Supreme Court nomination in the end (Clarence Thomas). What happened to Bork was the system working as intended. The minority preventing an extreme nominee but eventually allowing the President to nominate a slightly less extreme Justice.
Blocking a President from performing his Constitutionally granted right for over a year for no reason other than partisan politics was the greatest oath breaking I have seen in modern times. \
Nothing modern Democrats have done is even remotely comparable to this level of injustice - again compare Bork to the outright refusal to allow any nomination for over a year.
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Personally I believe this was such an unprecedented, egregious and life changing violation, the Democrats now have a free pass to reclaim their stolen Justice. If Trump gets a nomination, the Democrats blocking it is not obstructionism, it is justice to reclaim the unconstitutional theft of a nomination.