[GOPcapitalist]

If the Morill Tariff was such a big bone of contention for the southern political leadership then why didn't they secede in May 1860 when it passed the House?

It could have something to do with the fact that there was still an election up for grabs in November and that the push for a tariff could still be halted. The Lincoln and his party changed all that.

[Non-Sequitur]

It could have something to do with the fact that there was still an election up for grabs in November and that the push for a tariff could still be halted.

They could have killed it in the Senate regardless. Why the change?