[Hattie]

Based on which part of the US Constitution, did they decide that and vote that?

[mewzilla]

We’re no longer a republic.

Until our republic is restored, constitutional is whatever Deep State says it is.

[PghBaldy]

I suppose they could say slaves had representation, and they were not citizens.

[DSH]

Based on which part of the US Constitution, did they decide that and vote that?

I should imagine Article I, Section 2, as amended by the 14th Amendment, Section 2:

"Representatives shall be apportioned among the several States according to their respective numbers, counting the whole number of persons in each State, excluding Indians not taxed."

I.e. -- the "whole number" of "persons" in each state, not of "citizens" or even of "legal residents." I believe that would be the argument, constitutionally. That is to say, Congress has the discretion to define, by law, which "persons" are to be counted for purposes of apportionment, etc.

[PIF]

Based on which part of the US Constitution
—

you are waaay behind:
some of the Constitution was voided under Noxious Nixon;
a lot of the Constitution was voided under B. Clinton;
most of the rest under 0bama;
and the few remaining paragraphs erased under Biden.

There is no US constitution in effect at present.

[libertylover]

Based on which part of the US Constitution, did they decide that and vote that?

Yes, the Supreme Court ruled that Biden couldn't unilaterally forgive student loans, but he did it anyway (to buy votes with taxpayer money).