The states with narrower franchises would see the point you are making, and would, at the very least, insist on a specified franchise for the presidential races, to be the same throughout the United States. As to exactly what it would be, there could be a lot of haggling over that. About the most generous option would probably be something like "all white male persons over 21 years, and able to read, write and explain a section of the Constitution of the United States"
That would be a very strict franchise, and would never be accepted.
The number of eligible voters could actually go down in some places.
Right bleeping out. There is no way an egalitarian frontier state like Kentucky or Ohio is going to allow East Coast dudes to deny the vote to any of their citizens. And who is going to compose and administer these tests?
Secondly, even if states were allowed to do as you suggest, for many years to come there would be little incentive to do so. The decline of the Federalists meant that elections became very one-sided after 1800. It would be almost a quarter of a century before you got one whose outcome wasn't a foregone conclusion.
There were five elections in the next almost-a-quarter-of-a-century: 1804, 1808, 1812, 1816, and 1820. 1820 was, uniquely, uncontested. 1804 and 1816 might be considered to fall into the category of "foregone conclusion". But the elections of 1808 and 1812 were both strongly contested, especially 1812.
We have no popular vote numbers, but the electoral vote splits (ignoring some faithless and non-voting electors) were 129-47 (74%-26%) in 1808 and 129-89 (59%-41%) in 1812. The 1808 EV result was closer than the EV results in 1832, 1840*, 1852*, 1864*, 1872, 1920, 1928, 1932, 1936, 1940*, 1944*, 1952, 1956, 1964, 1980*, 1984, and 1988*, which includes five results where the popular vote difference was less than 10%. (Marked with *)
The 1812 result was closer than all those, and also 1828, 1844*, 1868*, 1892*, 1896*, 1900*, 1904, 1908*, 1948*, 1972, 2008*, and 2012*, including another nine <10% PV difference results.
Again, we don't have popular vote data for those elections. But the electoral vote data strongly suggests that popular support was
not extremely lopsided
throughout this period. Thus, even in a state where one party was dominant, that party would want to maximize the popular vote there, while in any state where neither party was dominant, both would seek to maximize voting by their supporters.
Voter turnout in 1860 did indeed rise from 1856 - but only from 78.9% to 81.2%.
"78.9% to 81.2%" of what? Male adult citizens? Registered voters?
The absolute numbers were up but this was presumably due to population increase rather than to any changes in franchise laws - if indeed, there were any such changes between 1856 and 1860.
4,051,605 is 78.9% of 5,135,114
4,681,267 is 81.2% of 5,765,107
That's an increase of 12.2%. Which
would be fairly close to general population growth for four years of that decade. I had forgotten how rapidly the US population was growing in that era: over 3%/year from 1840 to 1860.