Question

The ship has weather'd every rack,
the prize we sought is won;
The port is near, the bells I hear,
the people all exulting;
While follow eyes the steady keel, the
vessel grim and daring:
But O heart! heart! heart!
O the bleeding drops of red,
Where on the deck my Captain lies,
Fallen cold and dead.

—"O Captain! My Captain!"
Walt Whitman

The keel is the part of a ship that provides stability. What is Whitman referring to with the phrase “the steady keel”?

Lincoln’s re-election as president
the president’s death
the horrific injuries the soldiers suffered during the war
the idea of freedom that the United States stands for