The January 6 committee has now revealed how far Donald Trump was willing to go to prevent the peaceful and lawful transfer of power from his presidency to that of Joe Biden. Yet, his deadly serious attempt to upend American democracy also had a slapdash quality to it, reflecting Trump’s own impulsive nature and his reliance on a group of schemers – Rudy Giuliani, Mike Flynn, Sidney Powell, Roger Stone and John Eastman among them – of limited ability. It is not entirely surprising that Trump’s coup failed.

Another brazen GOP action, however, has succeeded – this one engineered by the Senate minority leader, Mitch McConnell, whose chess-like skills of political strategizing put to shame Trump’s powerful but limited game of bluster and bullying. The act to which I refer is McConnell’s theft of Barack Obama’s 2016 appointment to the supreme court, a radical deed that has dimmed somewhat in public consciousness even as it proved crucial to fashioning a rightwing supreme court willing to overturn Roe v Wade and to destabilize American politics and American democracy in the process.

McConnell is widely considered to be a cynic about politics, more interested in maintaining and holding power than in advancing a particular agenda. This is true up to a point. But it is equally true that McConnell has believed, for decades, that the federal government had grown too large and too strong, that power had to be returned to private enterprise on the one hand and the individual states on the other, and that the legislative process in Washington could not be trusted to accomplish those aims. Hence the critical role of the federal courts: the federal judiciary, if sufficiently populated by conservative jurists, could constrain and dismantle the power of the federal government in ways in which Congress never would. It was fine, in McConnell’s eyes, for Congress to be paralyzed and ineffectual on most domestic issues, as long as the GOP, when in power, stacked the federal judiciary and the supreme court with conservative judges and justices. Thus, across Trump’s presidency, McConnell pushed 175 district court appointments and 54 court of appeals appointments through the congressional confirmation process, far exceeding in numbers what Obama had managed during the second term of his presidency.

The supreme court, of course, was the biggest prize of all. The GOP had failed for 30 years to fashion a court to its liking, largely, it believed, because too many of its appointees – Sandra Day O’Connor, David Souter, Anthony Kennedy, and even John Roberts – had gone “rogue” on key issues: gay rights, gay marriage, affirmative action, Obamacare and, most of all, abortion. McConnell was worried that the GOP would fail again, this time under his watch as majority leader. Hence his willingness to steal an appointment that by historical practice and precedent belonged to Obama.

The tale of McConnell’s steal begins in February 2016, when Associate Justice Antonin Scalia, the lion of the judicial right, suddenly and unexpectedly died. Obama had just begun the last year of his presidency, and McConnell was entering his second year as Senate majority leader. McConnell immediately declared that he would hold no hearings on a new supreme court justice, regardless of whom Obama nominated. McConnell’s ostensible justification: it was inappropriate, he declared, for a president on his way out of office to exercise so profound an influence on America’s political future. Let the next president, to be elected in November 2016, decide who the nominee should be. That way forward would, McConnell argued, be a way of letting “the people”, through their choice of president, shape the supreme court’s future.

Obama nominated a centrist (and distinguished) jurist, Merrick Garland, in the hopes that it might soften McConnell’s and the GOP’s opposition. McConnell would not budge. He behaved as though no nominee had been put forward, allowing both Garland and Obama to twist in the wind across eight long months. We know the rest of the story: Trump won in November and nominated Neil Gorsuch to fill Scalia’s seat. Gorsuch was an arch-conservative jurist vetted by the Federalist Society. Knowing that he would be unable to secure the 60 votes necessary to bring closure to debate on the nominee, McConnell blew up the filibuster requirement for supreme court justices. Gorsuch was then confirmed (54-45) on the Senate floor.

Technically, McConnell had violated no laws. The Senate, by simple majority vote, has the authority to remove the filibuster from virtually any issue at any time. With regard to supreme court nominations, the constitution simply states that the president has the power to nominate justices and that the Senate’s advice and consent are required for confirmation. Still, McConnell’s refusal to authorize any action on Garland broke with 150 years of senatorial precedent and practice. The Senate had rejected nominees in the past, but only after debate and a vote. Some who were told they had little chance of winning such a vote had voluntarily withdrawn their names. A few had seen their cases deferred for a few months. But the last time a nominee was made to suffer Garland’s fate – consigned indefinitely to purgatory – was 1866. And that ancient case had a plausible justification that the Garland case did not: the nomination had come from a president – Andrew Johnson – on his way to impeachment and possible removal from office.

McConnell’s action was a calculated gamble. In early 2016, he did not know who or how strong the Republican nominee would be. But he regarded Hillary Clinton, the likely Democratic nominee, as vulnerable and beatable. And he expected his defiance of Obama on a supreme court nomination to fire up the GOP base. The stakes of the battle made the substantial risk worthwhile. McConnell distrusted Chief Justice Roberts because of the latter’s critical role in preserving Obama’s Affordable Care Act – another example, in the majority leader’s eyes, of a GOP-nominated justice going “rogue”. A Garland appointment might well have strengthened the centrism of the court, which is where Roberts wanted the power of his court to lie. McConnell wanted a court that would resist that drift, even if it meant breaking with a time-honored senatorial precedent. The end – a “truly” conservative court – justified the means.

Imagine, for a moment, that McConnell in 2016 had followed precedent and held hearings for and a vote on Garland. The moderate Garland might well have been approved and become Scalia’s replacement. Let’s presume, for the sake of argument, that the next two appointments went as they did: Brett Kavanaugh replacing the retiring Anthony Kennedy in 2019 and Amy Coney Barrett replacing Ruth Bader Ginsburg when the latter died in 2020. Had this scenario prevailed, the court would have entered its 2021-2022 term with three progressives (Stephen Breyer, Elena Kagan, and Sonia Sotomayor), one moderate (Garland), and five conservatives (Clarence Thomas, Samuel Alito, Roberts, Kavanaugh and Barrett).

This hypothetical court may well have declined to overturn Roe v Wade. Two of the votes that Samuel Alito needed to assemble his majority in the 2022 case repudiating Roe (Dobbs v Jackson Women’s Health Organization) were weak ones: Roberts and Kavanaugh. Roberts astonishingly admitted in his concurrent opinion that he thought it wrong to use Dobbs to overturn Roe, even as he was voting to do so. Kavanaugh, meanwhile, laced his own concurrent opinion with the anguish of someone deeply troubled by the affirmative vote for a Roe reversal that he, too, was casting.

What if Garland was sitting on this court rather than Gorsuch? Roberts, still in command of this court, may well have cobbled together a coalition to preserve Roe. He might have pulled a conflicted Kavanaugh to his side, and he might have worked out a deal with the court’s progressives (and probably Garland as well) similar in spirit to the one that Sandra Day O’Connor had engineered in Planned Parenthood v Casey (1992): jurisprudentially messy but workable as a compromise between America’s warring tribes. Were Garland sitting on this court, in other words, women in America today would still have a constitutionally protected right to reproductive freedom.

McConnell could not have foreseen in 2016 the particular way in which a majority of justices would coalesce in 2022 to overturn Roe. But his actions then were designed to lay the foundation for this sort of outcome. He resolved long ago that he would allow no principle to stand in the way of his pursuit of a rightwing court. Thus, in October 2020, he did not hesitate to abandon the arguments he made in the Garland case to jam through the Senate Amy Coney Barrett’s confirmation, even though Trump was much closer to the end of his presidential term than Obama had been to his in 2016. The ends – a rightwing court –justified the means.

McConnell’s machinations broke no laws. His 2016 supreme court steal, however, upended a century and a half of accepted senatorial practice. The price for the country has been high: damage to the court’s legitimacy, deepening cynicism about Washington politics, and a growing conviction that America’s ailing democratic system can’t be fixed.

• Gary Gerstle is Mellon professor of American history emeritus at Cambridge and a Guardian US columnist. His new book, The Rise and Fall of the Neoliberal Order: America and the World in the Free Market Era, will be published in April