Elections were a bit staggered back then but a deadlocked presidential election would have gone to the House some time between Nov 6 1860 and Mar 4 1861.
At the close of 1859,
Democrats held a majority in 15 delegations
Republicans in 15 delegations
1 delegation (TN) - “opposition.’ (Bell)
KY - 5 Democrats, 5 opposition (Bell)
NC - 4 Democrats, 4 opposition (Breckinridge)
MD - 3 Democrats, 3 know nothings (Breckinridge)
Oct 9 1860 - IN switched from D to R. (Lincoln)
DE switched from D to Unionist
(but voted for Breckinridge)
NJ switched from R to D (voted for Douglas)
For Breckinridge to have won in the House, Democrats would have held their ranks plus get at least one other state.
Interesting. Thanks.