Lincoln favored suffrage for educated African Americans and those who had served in the Union Army, but as of 1865 he was not willing to impose his views on that issue on the white South. But of course in OTL many moderate Republicans who did not insist on African American suffrage in 1865 were driven to do so within a few years by the massive violations of the freed slaves' rights. This *might* also have been the case with Lincoln. See my post at
https://groups.google.com/d/msg/soc.history.what-if/s7OCYnY41JM/XImp2BEjBMUJ It's from some years back, and the next-to-last paragraph is a bit more fatalistic than I would be today--but
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William C. Harris, _With Charity for All: Lincoln and the Restoration of the
Union_ (University Press of Kentucky 1997) is IMO the most interesting attempt
by a historian to examine the question of what Reconstruction policies Lincoln
would have followed had he lived.
He concludes that while Lincoln favored relatively lenient terms for Southern
whites, and was not about to impose black suffrage as a condition for re-entry
into the Union, nevertheless there was a difference between the policies
Lincoln would have followed and those Andrew Johnson followed in OTL (p. 269):
"[Lincoln's] exalted standing with southern Unionists and his experience in
dealing with them to achieve his purposes (for example, the dramatic
acceptance of emancipation by many formerly proslavery Unionists) would have
produced changes in the South different from those that occurred under
Johnson's administration. Lincoln...would have payed closer attention than
Johnson to the postwar plight of the freed blacks and white Unionists. His
influence on the side of bona fide freedom for blacks would have prevented the
kind of racially discriminatory laws, or Black Codes, enacted by several of
the Southern state governments after the war--laws that Johnson implicitly
endorsed...Though Lincoln had demonstrated his willingness to let bygones be
bygones, he would have made clear his opposition to an early return of rebel
leaders to political power, a position he had expressed during the war. Such
a stance would have prevented the rash pardoning that occurred under Johnson
during the summer and fall of 1865, arousing the Republican majority in
Congress against the new President." Harris thinks it is inconceivable that
Lincoln would have shown the lack of leadership under Johnson which led to
such outrages against black and white Unionists as the New Orleans riot of
1866.
I think Harris puts too much emphasis on Lincoln's plans during the war, and
not enough on how stubborn southern resistance to black rights might have
moved Lincoln "left" after the war, as it did many previously "moderate"
Republicans. He does at least mention the possibility on p. 275:
"Unforeseeable contingencies, such as terror campaigns to undermine black
freedom and loyal control, might have compelled him to adjust his Southern
policy to meet new realities." Lincoln by 1865 had no objection to black
suffrage--he indicated that he would have preferred it if the new Louisiana
constitution had given the vote at least to educated blacks and those who had
served in the Union Army--but was not at that stage ready to insist on it. I
think it is quite possible that Southern resistance to black rights would have
eventually driven him to such an insistence.
But whether Lincoln would eventually have become radicalized or whether he
would have maintained a conciliatory policy would probably have made little
difference for Southern blacks during the late nineteenth century and much of
the twentieth. The white South was determined on white supremacy, and no
amount of either conciliation or force would have stopped them from eventually
establishing white supremacy once federal troops were withdrawn from the
South--and Northern public opinion would not have sustained keeping the troops
there indefinitely.
In at least one respect, one can say Lincoln's death benefitted African
Americans. Without Johnson's blundering, which "radicalized" many moderate
Republicans, the Fourteenth and Fifteenth Amendments might never have passed.
To be sure, for decades these amendments did not do Southern blacks much good
(though at least the Fifteenth Amendment assured *Northern* blacks the right
to vote) but at least they provided the legal basis for the attack on white
supremacy once racial attitudes started liberalizing in the mid-twentieth
century.