Amendment 4 is on next Tuesday's ballot in Missouri:

Ballotpedia summary:

The amendment would require that citizen-initiated constitutional amendments receive a statewide majority of votes and a majority of votes in each congressional district in order to be approved. Currently, in Missouri, constitutional amendments are approved if a simple majority of voters approve the measure.

Also per Ballotpedia, by this Amendment's standards, none of the most recent citizen-led constitutional amendments (medical marijuana, abortion, etc.) would have passed, as all of them were rejected by Missouri's 7th district (Springfield and surrounding areas):

The Amendment also only applies to citizen-driven petitions -- not legislature-driven ones like Amendment 4 itself. This Amendment should obviously have to win in each congressional district to have any validity, right? Yet that's not required by design.

I'll obviously be voting an emphatic NO on this one. Just thought I'd share in case anyone had gotten up to speed on this topic yet.

This is one I’d vote no on simply because I don’t think you’d ever be able to amend the constitution again (which is really the goal of this). The state can legislate what they want and a statewide vote to overturn those decisions would fail each time.

For groups on both sides, it’s a terrible deal because issues they care about would never have a chance of passing if all 8 congressional districts needed to be in favor of it. Funny enough, say amendment 5 (end income tax) passed under current laws, it would need a simple majority (50+1). Under amendment 4, amendment 5 wouldn’t pass.

Yeah, I really can't understand how anyone other than a career politician would support this.

Right. It gives St. Louis a huge veto power over anything conservatives might push, being the only remaining Dem district. It makes no sense then even from the Republican side.