Just how far will Trump go to retain power?

If Putin has something on him that Trump simply doesn't want to see the light of day, I suspect Putin will turn the knife until the bitter end; and Trump will comply.

I believe there's a natural entropy for most GOP in the Senate to play their cards until the bitter end as well; simply as a matter of retaining power.

In light of how most "soft Constitutional guardrails" having been eroded in recent decades, I believe a core GOP faction in the Senate are willing - simply as a matter of being conditioned to play hardball - will exploit any "opening" that Trump might provide if they see in it a pathway to retain power. 

In general terms, the possibility exists for Trump to keep doubling down with the Senate still willing go along with him; however, each doubling will keep raising the stakes.