President Trump’s decision to forsake the Kurds will form no part of the House Democrats’ impeachment charges. But it could have an impact on Senate Republicans’ evaluation of his fitness, and their willingness to be his firewall.

For now, I do not believe the president is in trouble. The intensity of the opposition’s objection to Trump the man has always been far stronger than the persuasiveness of their case that Trump the president has committed impeachable offenses. Currently, Democrats offer nakedly partisan and unconvincing allegations of impeachable conduct; these may well be further discounted by ongoing Justice Department investigations of the Obama administration’s abuse of counterintelligence powers in monitoring Trump’s campaign. In a political process, if this is the state of play, the GOP-controlled Senate will give a quick back-of-the-hand to any impeachment articles voted by the Democrat-controlled House.

The landscape could change, though, if things get ugly in Syria. As we’ve seen this week, the dominant narrative is that Trump is responsible for the lethal abandonment of heroic American allies. That narrative is being driven not just by Trump’s opposition in the media and Democratic party but also by incensed Republicans, who supported American intervention in Syria and championed the Kurds. Things could become immeasurably worse for the president if what follows are weeks of powerful video images and on-the-ground reporting of atrocities by the Turks, and if the PKK predictably responds with terrorist attacks in Turkey that prompt Ankara to more aggression, potentially igniting a wider war.