Trump gets away with stuff that destroys a Democrat.
There is a simple reason for it.
Democrats express amazement and frustration that Trump does the most outrageous things, things that would have gotten Obama impeached, yet Trump gets away with it. Meanwhile, Democrats like Al Franken and NY Attorney General Eric Schneiderman resign promptly in the face of unproven accusations.
Trump has an affair with a porn actress, lies about it, arranges payoffs and lies about that, and yet some 85% of evangelical Christians support Trump. Republican voters support Trump. GOP officeholders support Trump. Trump shows up at a Prayer Breakfast and prays right in the middle of the Stormy Daniels mess, and somehow he is not shamed by the hypocrisy of it all.
It makes progressives' heads explode.
Their only consolation is that they think it exposes Republicans and Evangelical Christian moral scolds as flagrant hypocrites when they condemn the sexual immorality of others.
The double standard exists because Trump defined himself as a rule breaker, while Democrats who resist Trump defined themselves as reformers. Trump can break rules. Democratic reformers cannot.
There are two different brands doing two different things. Trump is the "bad boy" who defies conventional restraints of tradition, expert opinion, courtesies. When he does something flagrantly transgressive it affirms his strength. He has adulterous sex with Stormy Daniels because he wants her. It is the same Trump who can cancel an agreement with Iran because he wants to notwithstanding an existing deal, the desires of our closes allies, or the advice of supposed experts in the diplomatic corps.
On the other hand, Democrats, and especially Democratic politicians who aligned closely with women, have an opposite brand. They are the supposed white-hat good guys. Therefore, for them, any intimation of sexual impropriety breaks their brand, and they are revealed as hypocrites and their authority evaporates. Reformers have to be good.
Isn't Trump "good" when he attends the National Prayer Breakfast and says "praise be to God." No problem. Everyone knows it is just play-acting. No one believes he is becoming pious. He is voicing white Christian identity. It is just politics.
However, if Trump were to apologize meekly for offending blacks or immigrants--that would get him in trouble with his base. Trump sticks to his brand and script. Democrats who are accused of being sexually forward with women, or abusive in some way--that is the peril for them. They need to stick to their script, or else resign.
That is why there is the double standard.
What about the hypocrisy of GOP officeholders and Evangelicals? In fact, they don't feel hypocritical. They either deny the evidence--maybe Stormy Daniels is lying--or they observe that the Bible showed flawed people doing God's work. Trump is no worse than King David, so it is OK to stick with their man. He is the swashbuckling rule-breaking defender of the Faith, a bad man doing good.
Sex is unlikely to bring down Trump. Trump's aggressive sexuality affirms a notion of human behavior that fits into a conservative world view, one that humans are naturally bad and willful and that men--male sexuality in particular--is a powerful force. Liberals are more inclined to think men and women live in a single realm, but conservatives think that men are men and women are women--two realms. Trump affirms that notion. He grabs pussies, because he can. Strong men have strong libidos, and men who are leaders--winners--act on those desires, Donald Trump and King David, both. Women and Iran better beware.
Men like Franken and Schneiderman are goody-goodies, so they have to stay goody-goody.