1) Flake leaves GOP caucus 2) Dems make him majority leader 3) Subpoena Trump’s tax returns, protect Mueller 4) Confirm Kavanaugh, other judges 5) Pass bill retaking trade power (as per Constitution), block tariffs No legislation’s happening before midterms anyway Who says no?
Otherwise, Flake definitely doesn’t do it. He’s both anti-Trump and a staunch conservative, and his behavior indicates he places greater priority on the latter. He’d never risk blocking a conservative Supreme Court nom.