The remarkable public intellectual Michael Sandel has lectured on both sides of the Atlantic about the marketisation of many aspects of contemporary society, from the supply of human organs for transplantation to the provision of clean water. The latter is a good example of the market replacing “the commons”; free public access to clean drinkable water was one of the great achievements of the Victorian age in Britain. But the market has now trumped democracy itself, at least in the country of its greatest practitioner, the United States.

By the end of June this year, according to the Federal Election Commission, which oversees federal elections for the presidency and for the US Congress, $388m (£250m) had been contributed to the campaigns of presidential candidates for the 2016 electoral cycle. Almost half of the total came from just 400 wealthy donors and their families. Jeb Bush, brother of the former President George W Bush, has already raised $163m.

Even candidates without such august connections can raise very substantial sums. Popular Tea Party leader Ted Cruz, the junior senator for Texas, has already reportedly raised $37m from just three families. The huge accumulation of money to back, in particular, Republican candidates comes mainly from the top 1 per cent of wealthy Americans.

This dramatic change in the pattern of financial support for federal election candidates is a consequence of two Supreme Court verdicts by a conservative court, in which almost all significant decisions are made by a knife-edge majority of five justices against four. The verdict in the first case in 2010, Citizens United against the Federal Election Commission, allowed corporations and trade unions to contribute to political action committees without limit – provided only that the committee, now known as Super Pac, was not acting in conjunction with a particular candidate’s campaign. The only limits that remained at this point were over donations to individual candidates.

This, however, did not satisfy Shaun McCutcheon, a prominent Alabama donor. He made common cause with the Republican National Committee in a case to remove the limits altogether. The Supreme Court removed the limits in its verdict (again five to four) on 2 April 2014, and donations can now be made directly to candidates themselves. This verdict, like the earlier Citizens United decision, was reached in the name of the First Amendment on freedom of speech, with no requirement of any kind for equal time as between the competing candidates. In a country where access to the media of radio and television is determined by ability to pay, candidates with limited funds are at a huge disadvantage.

Republican presidential nominations Show all 9 1 /9 Republican presidential nominations Republican presidential nominations Jeb Bush Who he is: Brother of former President George W. Bush and son of former President George H. W. Bush, Mr Bush has formed a Political Action Committee and is exploring a presidential bid. He was the governor of Florida from 1999 to 2007. The issues: Mr Bush has indicated that his campaign would focus on the economy, foreign policy and energy. He is also known as a proponent of education reform. Getty Republican presidential nominations Marco Rubio Who he is: Mr Rubio is a US senator from Florida who has served since 2011. He is an early favourite to receive heavy donations from ultra-rich donors the Koch brothers. The issues: Mr Rubio has said the biggest issue facing the US in the near future is foreign policy and dealing with threats from China, Russia, North Korea and Iran. AP Republican presidential nominations Ben Carson Who he is: Dr Carson is a retired neurosurgeon, who became one of the most prominent physicians in the US. He has no political experience, but has formed a PAC to consider a run for president. The issues: A big proponent of smaller government, Dr Carson holds a tough stance on illegal immigration and is staunchly opposed to government involvement in health care. Getty Republican presidential nominations Ted Cruz Who he is: Mr Cruz has served as a US senator from Texas since 2013 and previously was the solicitor general of the state from 2003 to 2008. The issues: Mr Cruz is strongly against illegal immigration and figures to offer a presidential campaign heavy on foreign policy. He supports tough sanctions on both Russia and Iran. EPA/SHAWN THEW Republican presidential nominations Carly Fiorina Who she is: Ms Fiorina is the former CEO of Hewlett-Packard and a former executive at AT&T. She also was a 2010 nominee from California for the US Senate. The issues: Ms Fiorina, should she run, will campaign as a pro-business candidate whose background as chief executive of a major company proves she can handle the US economy. Getty Images Republican presidential nominations Mike Huckabee Who he is: Mr Huckabee was the governor of Arkansas from 1996 to 2007 and ran for president in 2008. An ordained Baptist minister, he also hosted a talk show on Fox News until early this month. The issues: Mr Huckabee supports tax reform and often touts the FairTax, which would eliminate income and payroll taxes in favour of a uniform sales tax. getty images Republican presidential nominations Rand Paul Who he is: Mr Paul has served as a US senator from Kentucky since 2011. He is a libertarian and son of former US Rep. Ron Paul of Texas. The issues: Mr Paul supports balanced spending by the government, unlike some of his peers in the Republican Party who oppose most government spending. He has been called an isolationist by some political pundits. AP Republican presidential nominations Scott Walker - OUT Who he is: Mr Walker has served as the governor of Wisconsin since 2011 and has long been mentioned as a potential presidential candidate. Mr Walker this week launched a PAC to prepare for a presidential run. The issues: Mr Walker opposes compromise with Democrats on key issues and would encourage increasing the fight against Isis. AP Republican presidential nominations Rick Perry - OUT Who he is: Mr Paul has served as a US senator from Kentucky since 2011. He is a libertarian and son of former US Rep. Ron Paul of Texas. The issues: Mr Paul supports balanced spending by the government, unlike some of his peers in the Republican Party who oppose most government spending. He has been called an isolationist by some political pundits. Getty

Republicans have waged a successful campaign to improve their position at the Congressional level too. In many states, turnout in such elections is low and a well-organised and funded campaign can carry the day. In the US, the boundaries of Congressional districts are determined by state legislatures, not by an independent boundaries commission. In some states, boundaries have been gerrymandered to determine the outcome. For example, concentrating the votes of African Americans or Hispanic Americans in a few districts, to render others marginal. It is an activity in which both major parties engage, but once the boundaries have been agreed by the legislature, changing the political complexion of the state can become very difficult indeed. One political analyst told me that winning a majority in Congress was now close to impossible for the Democrats.

Negative campaigning has badly affected voter turnout in the United States, as has the sense that money determines election outcomes. In the 2014 mid-term elections, the most expensive ever, voter turnout was the lowest for seven decades at 36.3 per cent nationwide. In 12 states – including New York, California and Texas – not even a third of the electorate bothered to vote. Cynicism and apathy are killing democracy.

It is imperative in a democracy that those opposed to the government of the day can cherish the prospect of peacefully changing its leaders and its policies. Otherwise the alternatives are some form of violent action, a revolution or a coup.

One of the constitutional subtleties of the UK has been the official status given to the main opposition party and its leader within Parliament – a status recognised by the only body permitted to broadcast political campaign material during a general election, the BBC. Once that position is overridden, the door is open to democracy in the modern world becoming plutocracy, democracy for sale to those with the means to buy it.