Hennessey posits that this partisan breakdown is why President Obama sat on the agreements for almost three years:
The two years of renegotiations were politically convenient for President Obama, as they allowed him to avoid asking Speaker Pelosi to bring up legislation that most of her caucus opposed....
All three FTAs split his party deeply with most of his partisan allies opposed. By taking two years to renegotiate the FTAs, he did not have to put his House allies in an uncomfortable position while he was relying on them to enact the stimulus, health care, and Dodd/Frank.Readers of this blog will know that I've been saying this for years now: the FTAs' delay was clearly a case of the President putting his own political interests above the interests of American exporters and consumers (and the US economy more broadly).
Hennessey also uses his analysis to make some broader conclusions about congress and "free trade." The most astute conclusion, in my opinion is that "[t]he [FTA] renegotiation and a Democrat in the White House provided more political cover for on-the-fence Democrats to vote aye. That would suggest these ratios are a free trade high water mark for the Democratic party."
I'm definitely inclined to agree there too, but I'd strongly caution against using FTA votes as a barometer for "free trade" support more generally. You may think I'm picking nits here, but this is a pretty important distinction if you're trying to measure partisan support for "free trade," not just FTAs. As you may recall, the FTAs were sold by the White House and congressional Republicans on purely mercantilist (exports only) grounds, and many Republicans who voted for the FTAs have supported or proposed anti-trade measures in the past. For example, 16 Senate Republicans recently voted for the horribly-protectionist China currency bill, and Sen. Jeff Sessions singlehandedly blocked implementation of the trade liberalizing GSP program last December. So while Hennessey's FTA analysis gives us a great idea about future congressional support for other trade agreements (e.g., the under-negotiation Trans-Pacific Partnership), and gives us a gauzy sense of which political party supports "free trade" more broadly, it probably shouldn't be used to determine future partisan support for non-FTA trade legislation. Unfortunately, GOP support drops significantly when a trade agreement isn't involved.