Found it. Douglas proposed that any speech that would irritate southerners be classified as sedition, and that Republican leaders, including Seward and Lincoln, who he specified by name, be jailed under it.
Quite amazing, when you realize that Douglas considered himself, and was considered by many others, to be a moderate. In point of fact, he was in the middle between those who wanted to expand slavery and those who wanted to limit or end it. As such, he got attacked by both ends of the spectrum.
And yet, he attended Lincoln’s inaugural, while others in his party plotted to assassinate Lincoln before he took the oath.