You can look at it this way. When the WTO agreement was passed, opponents worried that it would lead to a massive transfer of manufacturing jobs to China, which

You can look at it this way. When the WTO agreement was passed, opponents worried that it would lead to a massive transfer of manufacturing jobs to China, which could undercut the US with lower wages, laxer safety and environmental protection standard, etc. Supporters claimed that it would benefit the average American, not just the wealthy, and that the spread of a market economy would bring democracy to China, which would then pass labor and environmental protection laws similar to our own. What actually happened is that the WTO led to a massive transfer of manufacturing jobs to China, inequality in the US has increased, China has shown no interest in democracy, the working class there still enjoys low wages and poor working conditions, and they are now the largest polluter in the world. On top of that, the US as a whole has been weakened, and the fact that we have thrown away any chance of conditioning access to markets on the implementation of air pollution regulations looks ever more regrettable given global warming. I think it is reasonable to look at that and adjust your priors to trust TPP opponents more and TPP proponents less, even in the absence of any TPP-specific information.