01/09/2012 05:25 pm ET Updated Feb 02, 2016

Could a Constitutional Amendment Banning Same-Sex Marriage Be Passed?

Last week's Iowa Republican Caucus produced what effectively amounted to a tie. Mitt Romney came in first place with 30,015 votes, while Rick Santorum came in second, just eight votes behind him on 30,007. Both Republicans are on record as saying they favour amending the United States Constitution to define marriage as solely a union between a man and woman. In other words, both want to overrule Washington D.C. and the six states that currently allow same-sex marriage by banning it at the federal level.

It is, of course, laughable that candidates who claim to advocate "small government" and "less regulation" want to intrude on the private lives of American citizens and regulate whom they can and can't marry. It is, of course, hypocritical that they paint themselves at patriots with the same values as America's Founding Fathers and then seek to amend the Constitution that those founders painstakingly debated and wrote. I could write about either of these issues, but what interests me more is whether or not such a constitutional amendment is even possible.

Since the Constitution was ratified in June 1788, there have been 27 successful amendments. Ten of these are included in the Bill of Rights, ratified in 1791. Counting the Bill of Rights as a single amendment rather than 10 separate ones means there have only ever been 18 successful amendment movements in the last 223 years. These have included protecting freedom of speech (I), the right to bear arms (II), the right to trial by jury (VII), the abolition of slavery (XIII), and the granting to women of the right to vote (XIX). Only one amendment has ever restricted individuals' rights: that amendment introduced prohibition (XVIII) and was ratified in 1919, but it was repealed 14 years later by a further amendment (XXI).

Interestingly, while would-be Presidents Romney and Santorum say they are in favour of and would support a constitutional amendment banning same-sex marriage, presidents actually play no role in the passing of constitutional amendments. There are simple rules for amending the U.S. Constitution that require ratification by Congress and individual states. In the first instance, two-thirds supermajorities in the U.S. Senate and House of Representatives must pass a constitutional amendment. Once passed by Congress, an amendment must then be ratified by 75 percent of all states, whereupon it becomes law.

Let's start with Congress. A constitutional amendment banning same-sex marriage would require 290 votes in the House and 67 votes in the Senate. In the 2010 election, when Republicans regained control of the House on a wave of health-care-related Democratic ill will, they still only managed to win 242 votes to the Democrats' 193. In fact, since World War II, only three Congresses have witnessed one party holding more than 290 House seats, and on each of those occasions (1965-67, 1975-77 and 1977-79), Democrats were in the majority. Although a bipartisan vote is a possibility at any time, in my opinion, a constitutional amendment banning same-sex marriage wouldn't even make it out of the House. This is just as well, because such an amendment would undoubtedly fail in the U.S. Senate.

At the 2010 election the Senate was split 53 to 47, Democrats-plus-independents to Republicans. Twenty-three of the Democrats' Senate seats and 10 Republican seats will be contested in the 2012 election. In theory, if the Republicans retained all 10 of their seats and won all 23 of the Democrats' seats, they would have a Senate majority of 70:30, enough to pass a constitutional amendment banning same-sex marriage. In practice, however, Delaware, Maryland, New York, Rhode Island, and Vermont are safe seats for the Democrats, and as such, even a doomsday scenario wouldn't see a Republican majority over 65. After eight years of George W. Bush and with the election of Barack Obama as president in 2008, Democrats could still only manage 59 Senate seats. A constitutional amendment banning same-sex marriage is thus extremely unlikely to make it out of the Senate.

Finally, even if an amendment were to pass Congress, it would need to be ratified by 75 percent of all states. In practice, that means 38 states. Rick Santorum recently noted that amendments defining marriage as between one man and one woman passed in 32 out of 32 states where the question was placed before voters. Nevertheless, that still leaves him six states short. Furthermore, ratification by states has in all but one past instance always been done by state legislatures rather than by the people, and even now, after the 2010 elections, Republicans only control 26 state legislatures to the Democrats' 15.

In summary, then, a constitutional amendment banning same-sex marriage simply isn't realistic. Romney and Santorum might gain a few votes from haters who think they can override states' rights and impose their personal views on the electorate, but in practice it simply isn't going to happen. Moreover, Romney and Santorum are dishonest for pretending a constitutional amendment is something they can deliver. They can't.

Roughly 100 to 200 constitutional amendments are introduced in Congress each year, collectively amounting to tens of thousands since 1788. Given the incredibly high hurdles that have to be overcome, it's no surprise that so few become reality, and those that do are bipartisan issues defining fundamental human rights. I can't help but think that Romney's and Santorum's chances of passing a constitutional amendment would be better if they were trying to enshrine the right to same-sex marriage rather than ban it. Certainly their efforts would then be more in keeping with the sponsors of every previous constitutional amendment that remains law.