Seward would not have done as well as Lincoln. And if Douglas felt he had a chance of moving the election into the House, he probably would not have essentially abandoned trying to win in the latter days of the campaign in favor of trying to keep the south from seceding. To get the election into the House he would need to win California, Illinois and Indiana with Indiana being the pivoyal state IMO. The Vice President would almost certainly be Herschel Johnson, but the House would take a while to settle out between Lincoln, Douglas, and Breckinridge. I can't see Lincoln or Breckenridge winning the House, but I'm not certain if Douglas could get enough support either. March 4, 1861 could very well see Johnson being sworn is as Vice=President and Acting President pending a settlement of the election in the House.
I know how Breckenridge could have won.
Douglas could have taken a wrong turn in Evansville, Indiana
(*wink* At readers of the UPA... which hopefully I'll update soon.)