The United States Constitution rightfully has a venerated place in the history of democracy. Unfortunately, it also has a structural problem that will make it unworkable -- possibly in the very near future.
The Population Data:
Statista has a projection of U.S. population by state in the year 2040. I have serious doubts that any projection will be accurate as major weather events (like the one that displaced a huge number of people in Puerto Rico), drought, and other symptoms of climate change will likely cause unpredicted and substantial shifts. However, we go with the data we have, not the data we wish we had.
The data shows that the projected total population of the states of the United States is 381,975,542 (quite specific for a projection, I know). This excludes territories and the District of Columbia (which is projected to have a population greater than the six smallest states).
The eight largest states, California (12.64% of the total U.S. population), Texas (10.65%), Florida (7.39%), New York (5.60%), Pennsylvania (3.40%), Georgia (3.35%), Illinois (3.32%) and North Carolina (3.28%) will together represent approximately half (49.64%) of the total U.S. population. The smallest 26 states (i.e. a majority of states) will have 18.26% of the total U.S. population. The smallest 34 states (i.e. a two-thirds majority of states) will have 30.56% of the total U.S. population. The smallest state by population, Vermont, will represent 0.16% of the total U.S. population.
This is a change -- though not a huge change -- from how it is today. Current state population statistics show that the largest twelve states, California (10.35%), Texas (7.41%), Florida (5.49%), New York (5.20%), Pennsylvania (3.35%), Illinois (3.35%), Ohio (3.05%), Georgia (2.73%), North Carolina (2.69%), Michigan (2.61%), New Jersey (2.36%), and Virginia (2.22%) represent approximately half (50.81%) of the total US population. The smallest 26 states (i.e. a majority of states) have 16.26% of the total population. The smallest 34 states (i.e. a two-thirds majority of the states) have 26.95% of the total population. The smallest state by population, Wyoming, represents 0.15% of the total U.S. population.
The Problem: Senate Version
The United States Senate is comprised of 100 senators, two from each state. While senators are directly elected pursuant to the 17th Amendment, they are elected at a flat rate of two senators per state, regardless of population.
The Senate was established in Article I, Section 3 of the U.S. Constitution. No legislation can become law without a majority of the U.S. Senate (or with a tie, broken by 'yes' vote by the Vice President). The Senate has every power the House has, except the power to impeach and the power to originate spending bills. However, the Senate also holds a huge amount of power that the House does not, including:
The power to approve or disapprove of treaties by a two-thirds vote;
The power to approve ambassadors, other public ministers and consuls, judges of the Supreme Court, and all other officers of the United States by a simple majority vote; and
The power to remove an impeached President or other officers of the United States from office by a two-thirds vote following an impeachment in the House (without such a vote in the Senate, an impeachment does not cause any removal from office).
The upshot of this, in light of the current and projected population, is bad. Currently, senators representing only 16.26% of the total population control a majority of the Senate. Put another way, legislation or judges supported by 83% of the U.S. population can be rejected if the senators from the 26 smallest states vote to reject them. Legislation punishing large states (as the 2017 tax reform bill did by capping the state income tax deduction) can be passed by senators representing less than 17% of the U.S. population. Impeachment trials, treaties, and veto overrides can be passed by senators representing less than 27% of the U.S. population.
Oddly, this gets slightly better with the projected 2040 numbers, when the smallest 26 states will represent a total of less than 19% of the total U.S. population yet control a majority in the Senate. By 2040, treaties, impeachment trials, and veto override requiring two-thirds of the Senate will be controlled by senators representing less than 31% of the U.S. population.
Looking from the perspective of the biggest states, however, things get much worse over time. Currently, the 50% of the U.S. population living in the biggest states get a small 22% of the voting power in the Senate. However, by 2040, the 50% of the U.S. population living in the biggest states will get only 16% of the voting power in the Senate. While 22% and 16% seem to both be quite small, the drop to 16% represents a loss of more than a quarter of the power held by the half of the population living in the largest states.
When legislation and judges supported by 83% of the population now (or 81% of the population in 2040) can be blocked by senators representing only 17% of the population now (or 19% of the population in 2040), you no longer have a functioning democracy. When half of the population gets only 22% of the voting power now (and only 16% of the voting power in 2040), you no longer have a functioning democracy.
Revolutions have happened over such badly skewed representation, and if the trends continue, the risk of revolution in the U.S. -- particularly given the ease by which military grade weapons can be obtained -- is unacceptably high.
The Problem: Electoral College Version
The President of the United States is not elected by popular vote. Instead, the electoral college (the one created by the 12th Amendment to replace the version in the Constitution -- adopted instead of a national popular vote at least in part to preserve slavery) provides that (with the exception of Washington D.C., which gets the same number of electors as the smallest state by population, per the 23rd Amendment) each state gets one vote for every member of Congress, and of course no state is permitted to have less than one member of the House. That means that the minimum number of electoral votes each state gets is 3 -- or that 153 electoral votes (3 per state and 3 for D.C.) are assigned without regard to population. Since the electoral college has a total of 538 votes, this means that 28.4% of electoral votes are distributed without regard to population, and the remaining 71.6% are distributed based on population.
As the largest states grow larger and the smaller states represent a smaller percentage of the population, two competing risks grow. The first risk is that a small number of states can control the entire electoral college. Imagine, for example, an interstate compact between the twelve largest states: Virginia, New Jersey, North Carolina, Georgia, Michigan, Ohio, Illinois, Pennsylvania, Florida, New York, Texas, and California, which together represent 270 electoral votes. The compact states simply: "The winner of the majority vote aggregated among the twelve parties to this compact shall be given all of the electors in every state that is a party to this compact."
Boom. Now only twelve states are relevant to the presidential election. No matter what happens in the other thirty-eight states, the winner of the popular vote in twelve states becomes President. That is a very undemocratic outcome. I long harbored doubts about whether such a compact would work, as the Constitution gives state legislatures more or less plenary powers to determine how electors are chosen, and there is no reason to believe that a state unhappy with the outcome would not withdraw from the compact between the day the popular vote is held and the day the electoral vote is held. Nonetheless, a compact in this form poses a rather serious risk to democracy.
The second risk requires no interstate compact and will come to pass unless the Constitution is amended. In fact, the risk has already been realized -- although Republicans have held the White House for three of the five Presidential terms in this century, they won the popular vote only once in this century. It may already be the new normal that the winner of the popular vote loses the election most of the time -- but if it is not the new normal, it soon may be.
Currently, there are seven states with only three electoral votes -- Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont, and Wyoming. Those seven states represent 1.46% of the current U.S. population, but hold 3.9% of the electoral college voting power. If we include states with five or fewer electoral votes, we find fifteen states representing 4.8% of the population but 8.4% of the electoral college voting power. The difference between 4.8% of the population and 8.4% of the electoral college voting power means that voters in the fifteen smallest states get an extra 19 electoral votes not supported by their population size. This does not sound like a lot of voting power, but consider that many elections come down to just a few electoral votes. Both of George W. Bush's elections were closer than 19 electoral votes. When you consider that this inequality between population and electoral vote power can influence far more than 19 electoral votes (picking 3 or 5 electoral votes as my cutoff was arbitrary, after all), the risk that the popular vote winner will not become President is big -- and becoming bigger.
The Problem: Candidate Version
With the exception of Donald Trump and Dwight Eisenhower, modern Presidents have been drawn from the ranks of governors and senators. However, if half of the population -- and therefore half of the potential Presidents -- live in only eight states, there are only 24 people among half of the U.S. population who meet the traditional resume requirement for President. By contrast, there would be 126 people among the other half of the U.S. population who meet that requirement. Of course, we can count former senators and governors, but the ratio remains just as dismal.
Because the traditional pathway to the Presidency is now closed for many people in the populous states, we should expect an ever-increasing number of people to run for President with little or no political experience. This, too, should be a source of concern. Because of the combination of the high cost of running for office and the paucity of opportunities for people in large states to become senators or governor, we can expect a large number of wealthy people to run. For the lawyers reading this, don't put away your briefs about the Emoluments Clause just yet.
The Time Bomb:
The world will not end (I sure hope) in 2040, and the demographics will continue to shift. As global climate change makes much of the Southwest United States an infertile drought zone, and much of the Southeast United States an uninhabitable hot zone, the number of states with tiny populations will grow as the number of states with huge populations will change. At some point, it will become untenable for a state with a few thousand people to hold the same voting power in the Senate as a state with tens of millions of people (or more).
Solutions will be hard to come by, however: A constitutional amendment requires ratification by three-fourths of the states.