Well for starters Democrats didn't do it GOP did... You can say all day of what Democrats would and wouldn't do but the facts are GOP did it... They set the precedence...
Democrats have the popular vote in all three houses(Note 1) and yet the GOP picked the last three judges... This is highly undemocratic and will lead to unrest... This is effectively taxation with out (proper ) representation.... Democrats would be just correcting the scale so that the Supreme Court would reflect the will of the people more...
PR and DC... They pay taxes... Was US not founded on "No taxation without representation", it is there fundamental right to be able to vote in all levels of government with equal standing with other states... GOP were accused of suppressing citizens right to vote, this was rejected but is this not suppressing a citizens right to vote...
Using the excuse that I don't want those citizens to have there rights because they will not vote in my favour. Is this what USA was founded on?