This is from a letter my congress critter sent me, Rep. Martha Roby (R-AL). She is neutral on trade and is likely to vote no, but she doesn't spin it:
"Included in Congress' enumerated powers are those to levy taxes, duties, and to regulate commerce with foreign nations, while the president is charged with the authority to enter treaties and international agreements after seeking the advice and consent of the Senate. After many decades, TPA emerged as a compromise method for Congress to set legal boundaries and backstops for trade negotiations, but retains Congressional power for final approval of any trade deal. Various versions of TPA authorization have passed Congress since the Trade Act of 1974, and the most recent TPA agreement expired in 2007.
Ways and Means Chairman Paul Ryan (R-WI) introduced legislation that would reauthorize TPA, the Bipartisan Congressional Trade Priorities and Accountability Act of 2015 (H.R. 1890). This legislation requires the president to pursue a strictly outlined set of negotiating principles, including human rights issues and currency manipulation to promote more open, equitable market access. Any proposal would be available to view by the public for 60 days before presidential signature."
This demonstrates it would be the will of Congress for President Obama to pursue free trade agreements, not something the president tries to take from Congress.
Could you imagine the administration working for 6, 7, even 8 years on the most progressive trade policies ever, and we abandon our support for this president?