In 1860 Seward was the Republicans' leading candidate going into Chicago.
Now DiogenesLamp has previously posted a lot of fake news about goings on at the Republican convention in Chicago, but the fact is Republicans were not willing to nominate Seward for good reasons.
One is the very thing DiogenesLamp is most noted for: Republicans didn't like that Seward was a New Yorker.
Another is they believed only Lincoln could carry Illinois and other midwestern states, states which had previously been part of the Democrats' "blue wall".
If, with Seward the Republican nominee, those Midwestern states voted Democrat in 1860 then the election would be thrown into the House of Representatives and there Deep South Fire Eaters would make their demands, especially for something akin to the Corwin Amendment.
And the House would likely have elected Democrat Douglas President which means Georgia Governor Herschel Johnson would become President when Douglas died in 1861.
With a Corwin-type amendment ratified and Georgian Johnson as President, abolition in the United States would be off the table and expansion of slavery into free territories & states would be next on the Slave Power's agenda.
Lincoln said it this way:
Senator Herschel Johnson from Georgia (Douglas' VP) would become President in 1861 had Republicans nominated New York's Senator William Seward for President in 1860:
Yes, Lincoln bribed them. Offered promises of government jobs in exchange for support from pivotal delegates. Set the entire tone for his Crony administration and it's back door corruption with big business.
We see the consequences of it in the subsequent Grant Administration.