Given the consent of the governed being a requirement for a govt to be legitimate. At what threshold of congress approval do we say the govt is not being given consent ?

https://en.wikipedia.org/wiki/Consent_of_the_governed

Polled "congress approval" has no applicability, since we have direct popular election of both senators and House representatives (and, here, of state senators and representatives in Florida). The Constitution includes no direct provisions allowing disapproving citizens in California to disempower representatives in Maine (or, presumably, though I've never read the Florida Constitution, of residents of Tallahassee to disempower representatives of Miami).

Pretty sure the evidence is quite clear.

The first black president was elected promising change.

Now we have Trump who had no political background implying people want change

Choosing the least painful way to get screwed isn't consent.

assume the US voting populace was two sets of clones, 50% Mitch McConnell Republicans and 50% Nancy Pelosi Democrats - but the distribution always varied within a standard deviation (eg year to year or district to district or state to state). Maybe there's even some generational biases, where one set of clones is more common for a decade.

I think you'd find that pretty often, more than half the country disapproved of congress, even though, in the long run, each clone is equally likely as a voter regardless of geography, economic interest, etc. How could you design a voting system that's responsive to these variations?

This challenge gets more complex the more political alignments you account for.

Few people in an opinion poll of Congress are assessing their love of bicameral legislature. More commonly they're stating that they wish they could just have their way, regardless of opposing voices.

Special pleading aside, elections are how we gauge consent. What would be coercive would be if we deputized firms like Gallup and made their polls binding.

But putting principles to the side: your argument doesn't even hold up empirically. Americans have a very low opinion of Congress, but generally approve of their own representatives.

I strongly doubt the Founding Fathers intended that to mean "we should continue to deprive felons their rights to life, liberty, and property even after they have served their sentence".

In this case it matters less what the founders intended and more what the framers of the 14th Amendment thought almost 100 years later. You can read in Richardson v Ramirez a bit of a history of felon disenfranchisement; a reasonable summary might be: "there was a lot of haggling over the specific language of the clauses of 14A, but disenfranchisement for crimes was a consistent point of agreement".

Of course, that doesn't mean that it's right to disenfranchise felons (it almost certainly isn't), nor does it mean any state is obligated to disenfranchise (most states don't). It does however mean that it's not straightforward to appeal to the Constitution in arguing to get rid of it.

At the time of the Founding, most (or all?) felonies were punishable by death; I suspect that they would have considered release from prison with disenfrachisement to be quite merciful.

I could see probation and/or a required (and taxpayer funded) civics education course as part of a conviction; but I agree. Either the civil restitution and rehabilitation (I can dream we'll be a first world nation someday) are completed by the sentencing or the sentencing is insufficient and should be fixed in the law.

Permanent dis-enfranchisement is a way of ensuring someone remains ostracized from society and is forever given reason to work against it.

They were fine with depriving women and black people the right. I wouldn't expect them to have been super progressive on felons, either.