TPP and TTIP are about getting special deals for businesses that they would have difficulty getting through the normal political process. For example, oil and gas companies that think they should be able to drill everywhere may be able to get rules that prevent national or state governments from restricting their activities. This could mean, for example, that New York State would have to compensate potential frackers for the ban that Governor Cuomo imposed last week...

The pharmaceutical industry and entertainment industries will get longer and stronger patent and copyright protection. And the food and pesticide industries will be able to able to limit the ability of governments to impose safety and environmental regulations...

Best of all, these trade deals will set up a new legal structure that goes outside existing system in the United States and elsewhere. All the businesses that didn't think German or British courts could be trusted to give them a fair deal can turn to the investor-state dispute settlement tribunals established as part of these trade pacts. These tribunals will effectively make their own law. THE TRADE DEALS ALLOW NO APPEAL BACK TO U.S. COURTS OR THE COURTS OF ANY OTHER COUNTRY THAT IS INCLUDED. (Emphasis mine.)...

It takes lots of money to run a campaign. If the Democrats can show business that it can come through for it pushing massive trade deals like TPP and TTIP, then they expect that the businesses that benefit will reward them at campaign contribution time.

That's the basic story behind these trade deals which would otherwise look like both bad politics and bad policy for the Democrats. President Obama and other party leaders are prepared to ignore whatever harm the deals will do to the country and the world, with the hope that they amply rewarded in campaign contributions.