The only knockout blow to Trump is proof of collusion with the Russian government through Manafort’s existing network of entanglements with the oligarchs.
What PR are you talking about? The people who despise Trump already have ample reason to do so, and his supporters are looking for reasons to rationalize their continued support to him. Nothing Cohen has to say or reveal will measurably shift that.
@Moonbeam already nicely summarized how the GOP will dismiss and undermine Cohen as a rat.
The Stormy Daniels situation or white collar crimes, while inexcusable and grounds for impeachment, won’t be enough. Those lines of attack only feed the witch hunt narrative. Trump could even survive an obstruction of justice case. There is already precedence of this for an impeached President.
Collusion is the only charge that is politically inescapable.