Cruz has been scrutinized for alleged flip-flopping as of late, particularly on immigration. Rubio, whom Cruz has pummeled for supporting 2013’s failed Gang of Eight immigration bill, has launched his own offensive by pointing out that his and Cruz’s positions aren’t all that different, as evidenced by Cruz’s past support for raising levels of legal immigration. Rubio has also pointed to Cruz’s introduction of an amendment to the Gang of Eight bill that would have granted legal status to illegal immigrants after three years, which Cruz has argued was intended as a “poison pill” to kill the bill. But Cruz’s recent endorsement from Iowa representative Steve King, a star among conservatives, may help soften the blow of those criticisms.

While TPP may continue to influence the rhetoric of candidates looking to make inroads into the conservative grassroots, it is unlikely to prove a significant test for candidates. National Journal reported earlier this month that several Senate leaders have said the bill is unlikely to reach the floor of Congress until the very end of Obama’s presidency, if even then, given political concerns in both parties.

Ultimately, Cruz’s opposition to the deal makes for a double-edged sword, allowing him to pick off even more votes from the populist base that continues to warm to him, but also making him an easy target for challengers who would question his commitment to principle over political expediency. It’s a line of questioning he’d do well to prepare for — his future as the field’s self-defined purist could depend on it.