I think the pool of eligible non-voters is worthy of consideration- but not very much consideration. Historically, better than 58% turnout of voting age Americans does not seem to have been achieved since 1968.
The dynamism required to motivate the non voters is just as likely to cut both ways IMO
Voting Age Population (VAP)[clarification needed][8] Turnout[clarification needed][8] % Turnout of VAP[8][9]
1789
1792
1796
1800
1804
1808
1812
1816
1820
1824
1828 57.6%
1832 55.4%
1836 57.8%
1840 80.2%
1844 78.9%
1848 72.7%
1852 69.6%
1856 78.9%
1860 81.2%
1864 73.8%
1868 78.1%
1872 71.3%
1876 81.8%
1880 79.4%
1884 77.5%
1888 79.3%
1892 74.7%
1896 79.3%
1900 73.2%
1904 65.2%
1908 65.4%
1912 58.8%
1916 61.6%
1920 49.2%
1924 48.9%
1928 56.9%
1932 75,768,000 39,817,000 52.6%
1936 80,174,000 45,647,000 56.9%
1940 84,728,000 49,815,000 58.8%
1944 85,654,000 48,026,000 56.1%
1948 95,573,000 48,834,000 51.1%
1952 99,929,000 61,552,000 61.6%
1956 104,515,000 62,027,000 59.3%
1960 109,672,000 68,836,000 62.8%
1964 114,090,000 70,098,000 61.4%
1968 120,285,000 73,027,000 60.7%
1972 140,777,000 77,625,000 55.1%
1976 152,308,000 81,603,000 53.6%
1980 163,945,000 86,497,000 52.8%
1984 173,995,000 92,655,000 53.3%
1988 181,956,000 91,587,000 50.3%
1992 189,493,000 104,600,000 55.2%
1996 196,789,000 96,390,000 49.0%
2000 209,787,000 105,594,000 50.3%
2004 219,553,000 122,349,000 55.7%
2008 229,945,000 131,407,000 58.2%
2012 235,248,000 129,235,000 54.9%
2016 250,056,000 (estimated)[10]
Sorry for the poor quality of the cut/paste.
It is from this link:
https://en.m.wikipedia.org/wiki/Voter_turnout_in_the_United_States_presidential_elections