If the leaked details of Obama's expected action on immigration turn out to be true, the president's decision could improve the lives of more than four million immigrants directly, and millions more indirectly, according to estimates by the Pew Research Center.

One of the likelier proposals, which the New York Times reported last week, would allow parents of legal citizens and residents to acquire legal work documents. There are two possibilities reportedly being discussed for how widely this would apply: one option would cover parents who have lived in the United States for at least five years—another possibility is to require them to have lived in the country for more than a decade. In either case, the impact would be huge.

There are roughly 2.8 million unauthorized adults who have lived in the United States for at least 10 years and whose children were born in the country, according to Pew. And there are another 700,000 more who have U.S.-born children and who have lived in the country for fewer than 10 years but more than five. Add those two together, and we're talking about an estimated 3.5 million immigrants who currently don't have protection from deportation, but under the reported idea from Obama would be able to stay and work legally.

There's a separate possibility that the plan might also include relief for immigrants who arrived in the country as children and are still younger than 18 years old. Those, according to Pew, amount to another 650,000 people. If this group is also included in Obama's executive action, that would bring the total number of people affected by his action up to 4.15 million.

But this massive number doesn't account for the millions more indirectly affected by the reform: the families of those who would no longer be deported. Even the most conservative estimate—let's say 2.8 million undocumented adults are paired up and each couple has one child—suggests that more than a million children will suddenly not have to worry anymore about whether their parents will be deported.

Of course, we don't yet know what action Obama will take, only that he has promised to overhaul the country's immigration system without help from Congress. The reform Obama pushes through, if he pushes through immigration reform, could still look very different from the one leaked last week.

But deportation relief is a particularly important concern among Latinos in the United States. More than half of registered Hispanic voters say it's more important than even a pathway to citizenship for undocumented workers in a recent Pew survey. Obama likely knows this, and understands that signing an executive action on immigration might not only help millions of immigrants live without the fear of deportation—but also allow the Democratic party to cement itself, as my colleague Chris Cillizza notes, as the caretaker of Hispanic interests, a battle where Democrats have been losing a bit of ground lately.