An alternative to using the popular vote, would be to apportion presidential electors on the basis of citizen voting age population.
So the 28th Amendment would provide:
(1) Electors shall be apportioned among the United States and their territories on the basis of the number of citizens 18 years old or older. There shall be at least one elector for every 50,000 such persons, and each State shall be entitled to at least one. The apportionment shall take place one year prior to each presidential election.
(2) Electors shall be chosen by popular election by those eligible to vote for the larger chamber of the legislature. Time, place, manner, of elections shall be established by each State legislature, subject to override by Congress (same rules as for the House of Representatives).
(3) Electors shall meet as a single body to choose the president and vice-president. The president-elect and vice-president elect shall require a majority of the electors elected. The electors may meet at separate physical locations if contemporaneous communication is established.
(4) The 23rd Amendment is repealed. The District of Columbia shall be treated as a territory of the United States for purposes of this article of amendment.
If there was one district for each 50K people over 18, what would the 2016 map look like in terms of just state by state quantities of vote?
This would be the apportionment based on the 2010 ACS. Coincidentally, the total number is 4357, or almost precisely 10 times the number of representatives. California's apportionment of 460 electors would suggest that its fair share of representatives would be 46.
The ratio of CVAP/total is 69.5% for the USA, ranging from 61.6% for California to 78.5% for West Virginia.
Alabama 71
Alaska 10
Arizona 86
Arkansas 43
California 460
Colorado 71
Connecticut 51
Delaware 13
District of Columbia 9
Florida 263
Georgia 133
Hawaii 19
Idaho 22
Illinois 176
Indiana 94
Iowa 45
Kansas 40
Kentucky 65
Louisiana 67
Maine 21
Maryland 81
Massachusetts 93
Michigan 146
Minnesota 77
Mississippi 44
Missouri 89
Montana 15
Nebraska 26
Nevada 35
New Hampshire 20
New Jersey 118
New Mexico 29
New York 263
North Carolina 137
North Dakota 10
Ohio 172
Oklahoma 54
Oregon 55
Pennsylvania 192
Rhode Island 15
South Carolina 68
South Dakota 12
Tennessee 94
Texas 317
Utah 35
Vermont 10
Virginia 114
Washington 95
West Virginia 29
Wisconsin 84
Wyoming 8
Puerto Rico 55
American Samoa 1
CNMI 1
Guam 2
US Virgin Islands 2