The first Republican presidential debate is coming up August 6 in Cleveland, Ohio. Here are some questions the moderators might consider asking two of the candidates.

For Governor Walker of Wisconsin: Over the weekend you cited President Reagan’s 1986 tax reform, which created “two lower marginal rates,” as a model for tax reform. Reagan’s two tax brackets were 15% and 28% until President George H.W. Bush raised the rates. Would you bring back those two rates? If not, what rates would you seek? What if any deductions would you eliminate to broaden the tax base under these lower rates? Would the 28% rate also apply to capital gains? If so, how do you justify increasing the top capital gains rate from the current 23.8% top rate?

For Governor Walker: How do you justify a $250 million taxpayer subsidy for a new basketball arena for the Milwaukee Bucks?

For Governor Walker: You’ve been out on the campaign trail talking about an immigration policy that places a priority “on American working families, their wages.” What does that mean? Are you suggesting that immigrants undercut the wages of native-born Americans? What’s your evidence for that? If elected president, would you ask Congress to let in more legal immigrants than we do now, or fewer than we do now? Would you ask Congress to change the laws — family reunification, refugee status, green card lottery — that govern how people are allowed in legally now? If so, how? And since you described immigration over the weekend as “an issue where I have changed somewhat,” what should make us think that you won’t change on it some more after you get elected?

For Governor Walker: How would a Walker presidency be different from a Jeb Bush presidency?

For Governor Bush of Florida: How would a Jeb Bush presidency be different from a Scott Walker presidency?

For Governor Bush: You said you wouldn’t tear up a nuclear deal with Iran on day one of your presidency “Because on 12:01 on January, whatever it is, 19th, I will not probably have a confirmed secretary of state, unlikely, won’t have a national security team in place. I would not have consulted with our allies. I would not have had the intelligence briefings to make decisions.” What are the chances that such consultations and briefings will change your position about whether the Iran deal, which you condemned as “dangerous, deeply flawed…appeasement,” is a good idea? If what you do depends on who your secretary of state will be, can you name a list of potential occupants of that job in your administration?

For Governor Bush: You recently spoke in favor of a balanced budget amendment to the Constitution. Do you favor any other Constitutional amendments, for example, on abortion, same-sex marriage, a line-item veto, or flag-burning?

For Governor Bush: You apparently support increases in federal spending on space. Why, other than that you are from Florida, home of NASA’s Kennedy Space Center? Why is space exploration not something better left to the private sector? Would you exempt NASA from the federal hiring freeze and 10% workforce reduction that you proposed for the rest of the government?

For Governor Bush: You now say you don’t support a path to citizenship for illegal immigrants. As both a presidential candidate and as president, your brother George W. Bush did support such a path. Hillary Clinton is already criticizing you for opposing a path to citizenship. Why should the Republican candidate in 2016 have a position on this that Democrats can and will characterize as more anti-immigrant than that of George W. Bush?

For Governor Bush: You propose to change immigration law to eliminate the family preference for foreign siblings and elderly parents of Americans. Doesn’t that undercut Republican claims to be in favor of family values? You also propose increased penalties for businesses that hire illegal immigrants. Doesn’t that conflict with your push to reduce the regulation that Washington imposes on business? One reason you give in favor of changing the family preference is that other countries do it that way. Doesn’t that conflict with the idea of American exceptionalism? You also propose to use federal law enforcement funds to crack down on “sanctuary cities.” Doesn’t that conflict with the idea that local and state governments handle things best without a lot of mandates from Washington? Do you apply different principles to immigration policy than to other issues? If so, why?

Mr. Stoll is editor of FutureOfCapitalism.com.