Republican U.S. presidential nominee Donald Trump holds a campaign event at the Jacksonville Equestrian Center in Jacksonville, Florida U.S., November 3, 2016. REUTERS/Carlo Allegri

We know a lot about where Hillary Clinton and Donald Trump would try to take America as president. We don’t know everything. After a campaign that feels like it started in the middle of the Bush administration — the first Bush — questions remain, large and small, that the candidates have left scattered across their domestic policy agendas.

Those questions are revealing. The details of campaign plans don’t always become law, but they’re often the starting point for negotiations.

When candidates leave details unspecified, they’re being vague on purpose, either to put off tough legislative choices, tough political choices or both. They’re also suggesting what parts of their plans they might radically change, or discard altogether, if they reach the White House.

As the race draws to a close, here are the five biggest questions left unanswered by Trump, the Republican nominee, on domestic policy.

1. What would he replace Obamacare with?

There’s no way around this: The Republican nominee’s unanswered questions are often bigger — more fundamental — than his Democratic rival’s. Health care is a prime example. Like most in his party, Trump wants to repeal the Affordable Care Act. He promises to replace it with something “better” for consumers.

The details he’s released, though, don’t add up to what could realistically be construed as a conservative version of Obamacare, one that emphasizes market forces but still seeks to keep millions of Americans from losing insurance coverage in the event of repeal. He would let insurers sell across state lines, rely more on tax-free savings accounts for health care and attempt to reduce prescription drug prices by allowing imports of cheaper drugs from overseas.

Those ideas leave huge problems unsolved in the repealing of Obamacare; a leading conservative health care wonk, Avik Roy, calls them “empty rhetoric.” There are several more detailed conservative Obamacare alternatives. By stopping well short of them, Trump is able to make lofty promises about maintaining insurance coverage and keeping costs low, but voters aren’t able to evaluate whether he could deliver.

2. How many immigrants who are in the country illegally would he deport?

Trump vowed for a year to deport 11 million immigrants who remain in the United States illegally, an aggressive stance that was a driving force in his rise to the GOP nomination. He has since softened the stance. Maybe.

In recent months Trump has focused on a pledge to deport violent criminals and immigrants who have overstayed their visas, which likely means closer to 5 million people than 11 million. He said in a debate last month that his priority was going after “bad hombres.” But as recently as September, he reiterated his desire to deport all immigrants here illegally, the full 11 million, in a speech in Arizona.

The difference in those stances is a lot of money spent on immigration enforcement and a lot of impact on the economy, particularly the labor market.

3. What tax rate would he make some businesses pay?

Here is the very short version of what tax reporters call the Passthrough Mystery. Trump has proposed reducing the tax rate for businesses to 15 percent. He says that means all businesses, but his plans, after many rounds of revision, say otherwise: that at least some businesses will pay a higher rate, because their profit will be taxed as personal income for their owners.

It’s still unclear which businesses would have to do that.

At issue is a corporate structure known as a “passthrough entity,” which is popular among small business owners and also the companies in Trump’s own business empire. Even some individuals use the structure to report freelance income; for example, Bill Clinton does, for the money he makes from speeches. The question is how many of those entities would pay Trump’s 15 percent business rate.

Trump’s advisers have set some guidelines — essentially, that income previously considered business income will continue to be considered business income — that tax experts say don’t clear up the picture. The more businesses eligible for the lower rate, the more Trump’s tax plan will cost, which is why the question matters so much. By some estimates, the answer could mean piling as much as $1 trillion more onto the national debt. over the next decade.

4. What specific government spending programs would he cut?

Trump has promised at least $1 trillion in spending cuts over the next decade as part of his efforts to ensure his tax cuts don’t add to the budget deficit. He says he would not cut Social Security or Medicare, and he wants to increase defense spending. That leaves a relatively small corner of the budget as his only choice for cuts: non-defense discretionary spending. He has a method for applying those cuts, called the “penny plan,” but it doesn’t specify which programs would be chopped, so voters have no idea if he would be taking more from education, scientific research or any other part of the budget.

5. How he would ensure that no family would see a tax increase under his plan?

Trump’s tax proposal would, on the whole, cut taxes for Americans at every income level. But, because he gets rid of some deductions, including two that mean big money for large families, studies have suggested his plan could end up raising taxes on millions of families.

Trump’s advisers say they’ll make sure that’s not true — by simply instructing congressional committees writing tax law to ensure no one sees a tax increase under the plan. They haven’t said how the committees would do that, and it’s not clear how they could, short of allowing taxpayers to choose between a new system and the old one.