What was Lincoln's position on slavery up to the Civil War?

Lincoln was always personally against slavery, but he did not believe that the federal government could end slavery constitutionally.  As a candidate in the 1860 election, Lincoln only sought to limit the expansion of slavery into the land taken during the Mexican War.  Lincoln thought that slavery would die a natural death due to technological advancements--slavery would be ended by replacing laborers with machines.  If there was to be any freeing of the slaves through governmental intervention, Lincoln hoped that it would come at the state level with the slave-owners being compensated for their lost property.  Radical Republicans thought that Lincoln was too soft on slavery and abolitionists thought that a better candidate in 1860 would have been William Seward or Salmon Chase.  
Lincoln's stance on slavery did not change until around the middle of 1862.  He saw freeing the slaves as a war aim meant to weaken the Confederacy and by turning the war into a war to end slavery, it would morally isolate the South from its prospective European allies.