Popular election in defense of slavery?

I'm shocked to see such an inaccurate claim from Akhil Reed Amar.

When Madison's original proposal to have the legislature choose the executive - an idea natural to him as he was largely modeling the British system - was challenged, a counterproposal for popular election was shot down 9-1. All states, northern and southern opposed it except PA.

An electoral college was then proposed and also lost 9-1, with all states opposing it but MD.

Two days later NJ's Patterson reraised the idea of electors, suggesting 1 for small states and 3 for large ones.

The next day MA's Elbridge Gerry proposed an initial distribution of electors which was approved, with each region's states dividing on the issue - no regional polarization.

The issue came up again and again, defying easy resolution, but with the arguments all pitched at the level of practical political theory, not state interest. One of the most fervent opponents of popular election was MA's Gerry, who said "A popular election in this case is radically vicious. The ignorance of the people would put it in the power of some one set of men dispersed through the Union & acting in Concert to delude them into any appointment."

My internet is crappy right now and I'm reading very slowly loading notes of the convention on my little phone, so I'll stop there. I hope it demonstrates the point that this was not an issue that was really about slavery.

To put opposition to popular election down to Southern defense of slavery is shockingly ahistorical for a scholar of Amar's standing.