And there is a sure-fire way to do that. The rules committee should make it a condition of one's name to be placed in nomination for a candidate to post the last 10 years' tax returns, in full, including all schedules, at the Republican National Committee website.
There is a good reason (for all parties) to make this a requirement, regardless of Donald Trump. Any party nominating a presidential candidate would want to be as certain as possible that there will not be an October surprise. All nominees do extensive background checks on their prospective VP candidates for that very reason, including tax returns.
For those who might be interested in the nomination, they can post their returns. Many of the primary candidates already published them.
There are no circumstances under which Trump will reveal his taxes. His entire persona depends upon the myth he has created about himself and his wealth. His full returns would likely reveal those lies and also possibly show that he may have received amnesty under an IRS program to avoid jail for those who engaged in abusive, off-shore tax havens. As Trump cooked up scheme after scheme on his own, it is unlikely he would have refrained from participating in these.
Imagine, Trump having to run against an immigration policy providing a path to citizenship when he himself possibly received amnesty for breaking tax laws.
If the Rules committee enacts this change, Trump will likely whine and complain about it. But it will be his decision, not the convention's, to withdraw. He will not be forced out of the race. Convention delegates arguably pledged to Trump would not have to vote against him, and thus would not be charged with violating the will of the people.
And, Trump has, after all, said all along that he wants to release his returns, so the committee will be able to say truthfully that the only effect of its rule is to accelerate the process to ensure that the convention had performed adequate diligence on its presidential candidate.
This would also be face-saving for Trump. Rather than being rejected, he could spend the rest of his life claiming how much better he would have done than the eventual candidate and president, and that he only bowed out on principle. As ridiculous as it is to think that Trump has any principle, it would not be the most ludicrous comment he has made about himself.
So, Republicans, if you want to be rid of Trump, institute this rule.
If you do not, you own him.