Can the Republican be trusted with the nuclear codes? Why is the Democrat so secretive? These and other questions must be asked at the presidential debates

For Donald Trump

How can you be trusted with the nuclear codes?

A symbolic question, but one that goes to the heart of concerns about Trump’s suitability for the job of commander-in-chief. He has made a number of erratic comments appearing to suggest a cavalier approach to nuclear proliferation; he has also threatened to undermine both Nato and a longstanding commitment to non-nuclear allies in Asia. Combining all this with a general belligerence that terrifies even generals, Trump has much to do to reassure voters he is not a dangerous loose cannon.

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Did you support US intervention in Iraq and Libya?

Trump has tried to have his cake and eat it on the subject of Middle East policy, attacking Clinton for backing regime change in Iraq and Libya while implying he was opposed to both wars at the time. But though this real estate investor’s foreign policy views were not then widely sought out, there is a plenty of evidence to suggest he kept any opposition very quiet. Asked if he backed the invasion of Iraq, he said: “I guess so.”

Why would Mexico pay for you to build a wall?

The flagship policy of building a physical wall on the southern border is frequently embellished with a boast that Trump would make sure Mexico paid for its construction. A recent meeting with the Mexican president, however, made clear that this is highly unlikely. Trump appeared to mislead supporters almost immediately afterward and continues to ignore evidence that Mexican net migration into the US has dropped to near zero in recent years. The mechanics of his deportation policy are even vaguer.

Is there anyone you regret offending?

An open question that could lead Trump into uncharted territory. For over a year, the Republican nominee has outraged Muslims, African Americans, women, Latinos and disabled people with a series of ever-more outrageous comments. Any attempt to hold him to account for offensive language was dismissed as mere political correctness. Attacking the family of a Muslim war hero after the Democratic convention finally seemed to damage Trump in the polls, though, and prompted a half-apology. Who else will he say sorry to?

What evidence do you have against climate change?

Like many Republicans, Trump has repeatedly suggested that action to prevent man-made climate change is unnecessary because he does not “believe” it is real. He is even threatening to pull the US out of the Paris climate accord. Yet in the face of overwhelming evidence from world scientists, surely the onus is now on skeptics to prove their claims with facts and numbers of their own. What proof does Trump have that climate change is a “hoax”?

Trump is doing well if…

… he can convince viewers at home that he is not crazy. This low bar for success is a big cause for concern among Democrats. Trump has come a long way despite erratic and unpleasant behaviour on a unprecedented scale in modern politics. If he can walk offstage with people thinking he is not quite as erratic or rude as they thought, then it could make all the difference.

For Hillary Clinton:

Facebook Twitter Pinterest Hillary Clinton speaks in Philadelphia. Photograph: Matt Rourke/AP

What single policy should your campaign be known for?

Harder than it sounds, or should be, this question gets at a weakness which many critics feels lies at the heart of the campaign. Instead of one signature issue, Clinton has dozens of detailed policies on a host of subjects. It may make her a great president one day, but for now voters struggle to understand what slogans such as “stronger together” mean in practice. If Clinton were forced to pick one concrete thing for viewers to remember her for, what would it be?

Do you believe in globalisation?

Over many years in public life, the former secretary of state has understandably embraced an evolving set of economic positions. But few have come further than Clinton on the subject of free trade deals and the damage they may or may not have done to American manufacturing. She says she opposes the Trans-Pacific Partnership now proposed by Obama, but is it a principled opposition or a mere pragmatic response to Trump? Are there limits to the benefits of globalisation for US workers?

How would your counter-terrorism policy differ from Obama’s?

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In the face of continued terrorist attacks, the issue of “defending America” will be top of Monday’s agenda. Yet Clinton risks being caught between defending the legacy of an Obama administration in which she served and acknowledging that not everything is working out well right now. How would she defeat Islamic State? Would she be more or less hawkish in Iraq and Afghanistan? If nothing changes, then Trump may be able to pin her to a range of foreign policy failures.

Why are you so secretive?

From emails to pneumonia, Clinton has repeatedly got herself into trouble by going out of her way to hide information from the public. The obvious question is: what does she have to hide? The usual explanation is that Clinton has been on the receiving end of so many smears over the years that she has learned to be cautious, but this should also teach her to be wary of cover-ups. Why should someone who ignores medical advice to rest, or legal advice to keep email on government servers, be trusted to take wise decisions in office?

How would you reduce income inequality?

Supporters would argue that Clinton has provided many answers to this question: from infrastructure spending and a jobs program to minimum wage increases and taxing the rich. Yet many still wonder if a campaign so heavily funded by America’s rich and powerful really understands or is committed to helping its middle class. Her answers may be more nuanced than Trump’s crude protectionism, but they need to cut through with voters if she is to blunt his appeal in the rust belt.

Clinton is doing well if…

… Americans finish the debate with a clearer sense of what she stands for. Increasingly, the campaign has become defined by what it stands against – principally Donald Trump. While this is highly effective at motivating Democrats, it remains to be seen if this is enough to win over independent voters. Clinton needs to show them, not tell them, that she is on their side.