Will be interesting to see. Gotta think the Civil Rights Act would be right near the top.

@PoloHoleSet - it wasn't even in the list of top 10 most divisive congressional votes. What's your basis for thinking it was unpopular other than political prejudice?

The establishment resistance to integration before the passage of the laws, widespread overt and "covert" resistance to the laws. The fact that an entire portion of the nation felt strongly that such equality was an affront to traditions and natural order. The fact that many still feel and act this way today. The fact that the Democrats went from dominating the South, electorally to being dominated in the South, electorally, after Nixon and the GOP decided to use their "southern strategy" and welcome those who felt disaffected by the Act.

I would guess something in the civil war or reconstruction, though the spark of the 27th amendment might have better data.

@PoloHoleSet - as I said, you may want to try relying on data and not your prejudices that label everyone a "racist". As per pbs.org/newshour/updates/… (hardly right wing bastion), Pew poll had 58% approval of CRA in 1964. That's way way way above less popular laws like ObamaCare or never-passed-TrumpCare

Maybe you should not rely on your own prejudices about my opinions and read less into comments, not assertions, that I make. See that lone up-vote? That's mine, because I think it is an interesting question that will yield some enlightening answers. Also, a top ten list of divisive Congressional votes may or may not reflect widespread attitudes of the general populace.

Abolition of slavery and Obamacare likely are good contenders, as might be the various bailouts from 2008-2009.

@dennis I would expect one of the latter, abolition has a potential problem as an answer of whether it has any reliable polls. I'll check

A possible candidate would be Prohibition, but it too lacks polls.

Yea, I'd say Prohibition would be way up near the top of the list.

@user4012 FYI, 55% currently favor the ACA. Also, one would think the civil war we had would be some evidence that we weren't exactly united on the whole 'equal rights' think in this country.

Most unpopular laws don't become unpopular until the effect hits the populace. Wilson's income tax to finance WW1 is still with us, and fairly unpopular. Prohibition... rescinding it became a rallying cry by 1932. As for unpopular at the time of passage: Obamacare got the tea party a lot of votes, as much from the heavy handed nature of its authoring - despair over the failed economic model and skyrocketing costs is just starting to hit now.

@blip - Somehow, I doubt that civil war was so much about civil rights for most of the populace on Confederate side (as opposed to, y'know, plantation owners wanting to get free labour and random people not wanting Federal DamnYankees sticking their noses in on general principles as well as general tribal identity). But, admittedly, i'm less familiar with that period than with some others in history, so I could be wrong.

"so I could be wrong" wait...what? Are you mellowing with age? :)

@blip - that's exactly why the question asks about passage time. ACA got more popular (though I suspect in another 20 years it would get markedly less popular if left alone, as Millenials start having to pay for the Baby Boomer medicare). Prohibition less popular.

@tj1000 yet it's getting more popular...so I dunno.

Come to think of it...this maybe just isn't a great question. The more I ponder things, the more I can think of all sorts of laws regarding issues that have been massively divisive...legalizing marijuana...suffrage...labor laws...abortion...wars...I'm thinking at best this question can only produce a long list of answers.

@blip - that's because it was purposely designed to be front-loaded with benefits and the "will pay for this later" backloaded ages later. Same idea as over-promised DC pensions from state governments, which never got funded. Guess who'll be unhappy to pay them when they start needing bailouts (I'm guessing same 20 year horizon)

Let us continue this discussion in chat.

@blip - yet only one answer will be correct, since popularity is LITERALLY measured in linear way and only one can be "most".