Corker = He believed he would have greater moral authority to say it was bad if he had voted for it. Also, he thought he could convince a supermajority to still do the right thing once the default number of votes was inverted (66 to stop vs. 66 to pass a treaty (which he also didn't think could be forced to be considered as a treaty)).
Both are lame and ultimately helped his wife's CFR/Goldman Sachs wife get what she wanted for her employer(s).
TPA = He thought it was good, but after voting for it initially, the bill went to conference with the Senate and Cruz said those tweaks went too far.
Corker = He believed he would have greater moral authority to say it was bad if he had voted for it. Also, he thought he could convince a supermajority to still do the right thing once the default number of votes was inverted (66 to stop vs. 66 to pass a treaty (which he also didn’t think could be forced to be considered as a treaty)).
Both are lame and ultimately helped his wife’s CFR/Goldman Sachs wife get what she wanted for her employer(s).