If there was a Democratic taboo in Chicago, Gaza would be it: Don’t mention the war. Stray dissenters have had Palestinian flags taken away; a hijab-wearing protester was drowned out by chants of “We love Joe” and hit with a Biden placard after interrupting the president’s speech; permitted demonstrations are quarantined some distance away. Even to raise America’s most controversial foreign policy issue is to tempt fate.

Yet silence is Kamala Harris’s wisest option. As Biden’s vice-president, Harris cannot break openly with her boss. The last time this dilemma arose was in 1968 when Hubert Humphrey, Lyndon Johnson’s number two and the Democratic nominee, agonised on whether to call for a halt to the carpet bombing of North Vietnam. Prevarication helped cost Humphrey the election.

The Harris equivalent would be to threaten an arms embargo unless Israel agrees to a ceasefire. Such a stance would undercut Biden, who last week waved through yet another $20bn arms package for Israel. Even if Biden encouraged Harris to play bad cop to his good on Israel, silence would still be her best campaign stance.