1860 election using popular vote with a runoff

[rob in cal]

Assuming everything else was the same, but the US had a french style presidential election system, who would have won a runoff between Lincoln and Douglas.  I'd have to pick Douglas as he'd pick up the vast majority of Breckingridge and Bell voters in the runoff, enough to overtake Lincoln's ten point lead from the first round.

[True Federalist]

I wouldn't be certain of that, especially in the case of Bell supporters.  They were mainly ex-Whigs who wanted to paper over the slavery issue.  Some will stay home rather than vote for a Democrat and others, especially in the north, would vote a fellow ex-Whig than a Democrat.  You'll also have a fair number of Breckenridge supporters who stay home as they don't see any difference between the two and would rather just go ahead and get secession in place.

I think it would be a close race, close enough that I could see some states decide to secede before the runoff took place rather than take their chances, in which case, Lincoln wins, otherwise, Douglas probably wins in a squeaker.