For now, the only way out is through — together.Donald Trump, the erstwhile Democrat, independent, and member of the Reform Party, finally has a fixed partisan identity.The president may be besieged, unpopular, and prone to lashing out self-destructively, but all of this cements his bond to his party rather than erodes it. Commentators who ask wishfully and plaintively, “When will Republicans dump Trump and save themselves?” are missing the point: Trump’s weakness makes him more Republican than ever before.It was possible to imagine Trump, with a head of steam after his upset victory in November, cowing swamp-dwelling Republicans and wooing infrastructure-loving, anti-trade Democrats into supporting a populist congressional agenda. Maybe this was always a pipe dream given the instantaneous rise of the #resistance against him. But this scenario would have required a strong, focused president marshaling his popularity and driving #Congress.We’ve seen close to the opposite. And, of course, there’s the so-called Russia investigation. “Russia” is a misnomer. The controversy is now shifting from being about supposed Trump-campaign collusion to alleged obstruction of justice and whatever else special counsel Robert Mueller dredges up in what will probably be a free-ranging, years-long investigation.So, whatever Trump’s true ideological predilections, there’s no place for him to go. Make deals with the Democrats? At this point, Democrats are more likely to cooperate with Sergey Kislyak on an infrastructure package than with Donald Trump.Dump or triangulate away from Republicans? Well, then who would do scandal defense, besides a handful of White House aides and outside media loyalists? Imagine what the Comey or Sessions hearings would have looked like if Republicans had joined Democrats in the pile-on.