The longer the fight over the returns continues—especially if Trump loses in the lower courts but appeals and appeals again—the more likely it is that Americans will assume the worst.

Read: What Trump’s 2005 tax returns reveal

Trump already suffers from a wide and deep public-opinion disbelief in his integrity. In September, Gallup asked respondents to rate Trump’s ethics compared with those of other presidents. Sixty-eight percent regarded him as less ethical than Ronald Reagan; 58 percent as less ethical than Barack Obama; and 52 percent as less ethical than Bill Clinton.

Trump even suffers in comparison to Richard Nixon: 43 percent rate Trump as less ethical than Nixon, while only 37 percent rate him higher.

Quinnipiac University produced even more troubling results in March. Sixty-five percent told pollsters that they regard Trump as dishonest, the worst honesty number yet recorded by any survey. Sixty-four percent of Americans believe that Trump committed crimes before becoming president.

It’s often assumed that Trump has a solid 40 percent base. But that’s not true on ethics matters. Ethics surveys reveal a split between strong supporters and softer supporters.

When the Pew Research Center asked in January whether Trump was separating his business interests from his official duties, only 28 percent expressed strong confidence that he was doing so. Another 13 percent described themselves as “somewhat” confident. While 66 percent of conservative Republicans expressed strong confidence in Trump’s integrity, only 39 percent of self-described moderate Republicans did so.

Read: What is Trump hiding?

It’s unrealistic to imagine a split within the GOP over these issues, but it’s easy to imagine a continued melting away of Trump’s support on questions of ethics. Nearly two-thirds of Americans now agree that Trump should release his tax returns, again according to Pew.

Polls will not bend Trump on an issue as seemingly existential to him as keeping his tax returns concealed. But the issue of the tax returns may bend Trump’s polls.

Over the next weeks, Trump will be fighting multiple financial-disclosure fights. He has intervened to stop Deutsche Bank from complying with a congressional subpoena of his bank records. He threatens to fight to prevent Special Counsel Robert Mueller from testifying about Trump’s Russia connections. He’s already lost the first round of the emoluments-clause lawsuit filed by the state of Maryland and the District of Columbia.

As Trump fights to conceal his financial records, loses, appeals, and loses again, it becomes progressively more plausible to Republicans that those records conceal damaging revelations about serious wrongdoing. Trump is ultimately fighting to prove he’s not a crook. He can postpone delivering the records that would prove the matter one way or another. But as he fights to postpone the inevitable, he risks convincing voters that they do not need a subpoena to read his guilt.