Between them, Barack Obama and John McCain participated in more than 40 televised debates with their respective Democratic and Republican competitors over the course of 2007 and 2008. They were asked questions about topics from the serious (Iraq) to the frivolous (flag lapel pins). But to my knowledge, and I watched as many of these confabs as a normal human could be expected to endure, the men and woman bidding to be the next US president weren't asked a single direct question about the current administration's use, and misuse, of executive power.

This says something depressing about America's agenda-setting media corporations and their stars. For when the historical assessments of the Bush administration are delivered, there's little doubt that, while the list of its crimes against democratic practice will be long and the competition for worst transgression stiff, its abuse of executive authority will occupy a special place.

The men who founded the United States feared nothing more than an all-powerful executive that could, at its whim, define crimes against the state and detain those so accused without their even knowing of what exactly they were accused. The constitutional system of checks and balances and the bill of rights were written expressly to protect citizens from such an executive. Several wartime presidents have tested the limits of those instruments, and some more blatantly than George Bush. Franklin Roosevelt put Japanese-Americans in camps on mere suspicion that their nationality would render them loyal to the enemy combatant.

But democracy is about trying over time to perfect the union, and so, after Richard Nixon's various crimes against the state, we thought we'd reached the consensus that executive power had to be carefully checked, and we took some steps to do so. But everyone didn't agree with that consensus. There were young men, some then working in the administration of Nixon's successor, Gerald Ford, who saw the post-Nixon reforms as usurpations of executive power. Two of these young swashbucklers were Dick Cheney and Donald Rumsfeld.

They had to bide their time, but, three decades and a major terrorist attack later, they saw their opportunity. They put into place precisely the policies that the founders had feared. They gave themselves the power to declare people, including citizens, "enemy combatants" and to hold them indefinitely without specific charges. Nearly 800 people so designated were sent to Guantánamo Bay. No one seemed to have the power to stop it.

But someone did. Last week, the supreme court told the Bush administration, for the fourth time in as many years, that its practices were unconstitutional. The current decision, in a case captioned Boumediene v Bush, is a response to a response. After the third anti-Bush ruling, in 2006, the administration pushed a law through Congress that grudgingly respected Geneva convention rights for foreign "Gitmo" detainees, but denied them the right of habeas corpus. The law was challenged, and the supreme court, yet again, said to Bush: you are acting outside the constitution and you must stop.

When we talk about the presidential election, we talk about race and age and Iraq and the economy and healthcare. When we speak of the supreme court at all, we refer chiefly to abortion rights. The president, of course, appoints the court's justices. There are nine. They leave the bench either voluntarily (retirement) or involuntarily (death). One is 88. Another is 75 and has been living with a colon cancer diagnosis for about a decade. A third is 72 in July, and a fourth is 70 in August.

All the above, incidentally, are part of the wobbly majority that, by a 5-4 margin, ruled against Bush and for the constitution. The rightwing anti-constitutional minority is much younger (Chief Justice John Roberts, appointed by Bush, is just 53).

You don't need to be an insurance actuary to see what I'm getting at. The next president, if he serves eight years, will almost certainly appoint one, two or maybe even three justices, who will play a large role in shaping an anti-terrorism policy that is both effective and legal. So what might our two candidates do?

McCain used to be a constitutionalist. He used to say we should close Gitmo. Last week he said the court had just issued "one of the worst decisions in the history of this country". Considering that the supreme court spent most of the 19th century upholding slavery and segregation, that's saying something. He complains we'll see a flood of lawsuits, which is true, but that's the administration's fault for writing bad law.

Barack Obama, who to put it mildly doesn't stand to gain politically from defending the rights of terrorism suspects, drew a sharp distinction with McCain: "That principle of habeas corpus, that a state can't just hold you for any reason without charging you and without giving you any kind of due process - that's the essence of who we are." Obama's apparent seriousness on these questions is supported by a statement he made in May on what he hoped to accomplish in his first 100 days. Without prompting, he included a pledge to "review every single executive order issued by George Bush and overturn those laws or executive decisions that I feel violate the constitution".

I don't know how many votes this will net him. But I do know that, if he becomes president, the nation and the world will be grateful.

·Michael Tomasky is the editor of Guardian America

michael.tomasky@theguardian.com