I keep hearing that, on some geopolitical level, it will marginalize (or slow the resurgence) of China.
As devastating as it will be to US manufacturing, wages, and our environment, the part I fear most is how it will further enshrine the power of mult-national corporations.

Seems like a present-day economic version of the Vietnam era quote "It became necessary to destroy the town to save it.".

"Save it" for some short term profit-harvesting, I guess.

And not for much else.

Do you ever ask yourself why Obama is in favor of TPP? Does he have a history of siding with Corporate America over the greater good of the lower and middle class? Might it just be that he, who is an intelligent man and who has studied this subject far more than any poster on DU, thinks this is good for (A) America and (B) the world?
Most objective articles I have read, by non-partisan economists and experts, accept that free trade is absolutely necessary in the modern world economy. The jobs that have been lost cannot be brought back because they would never be competitive in an advanced economy like the US. If free trade agreements had a role in moving those jobs offshore it was just an acceleration of a process that was going to occur inevitably.
Not trying to ruffle any feathers, and I do realize that this is a minority opinion here. Flame away, friends.

...wisdom of my own to offer. I have asked myself your question several times. If someone as intelligent as President Obama is in favor of this, is there something he understands about it that we do not? I am generally inclined to trust his analysis of issues.

Krugman was most surprising to me because he was sort of for it (Globalization) for quite some time, and in some ways still is. However, he seemed to wake up to the political realities; he's basically called this "free-trade" crap a scam perpetrated by the elites. From March, 2016:

But it’s also true that much of the elite defense of globalization is basically dishonest: false claims of inevitability, scare tactics (protectionism causes depressions!), vastly exaggerated claims for the benefits of trade liberalization and the costs of protection, hand-waving away the large distributional effects that are what standard models actually predict. I hope, by the way, that I haven’t done any of that; I think I’ve always been clear that the gains from globalization aren’t all that (here’s a back-of-the-envelope on the gains from hyperglobalization — only part of which can be attributed to policy — that is less than 5 percent of world GDP over a generation); and I think I’ve never assumed away the income distribution effects.

Furthermore, as Mark Kleiman sagely observes, the conventional case for trade liberalization relies on the assertion that the government could redistribute income to ensure that everyone wins — but we now have an ideology utterly opposed to such redistribution in full control of one party, and with blocking power against anything but a minor move in that direction by the other.

So the elite case for ever-freer trade is largely a scam, which voters probably sense even if they don’t know exactly what form it’s taking.

... it is fair to say that the case for more trade agreements — including TPP, which hasn’t happened yet — is very, very weak. And if a progressive makes it to the White House, she should devote no political capital whatsoever to such things.