WASHINGTON, DC - AUGUST 09: U.S. President Barack Obama delivers a statement about the ongoing U.S. military actions and humanitarian drops in northern Iraq before leaving the White House August 9, 2014 in Washington, DC. Obama is traveling to Martha's Vineyard for a two-week vacation. (Photo by Chip Somodevilla/Getty Images)

WASHINGTON -- As the Obama administration gets ready to unveil a potentially wide-ranging new policy on deportation relief, Democrats are making the case that there is political cover and precedent for him to go big.

In a newly released memo, the Democratic opposition research firm American Bridge highlights 10 instances in which past presidents have used their authority to apply selective prosecution of immigration laws. More often than not, those instances targeted specific populations caught up in complex and dangerous foreign policy crises. But immigration lawyers sympathetic to the White House say that these actions still provide sound principle on which the current administration can act.

"Any president ... that is ultimately responsible for law enforcement has wide, wide latitude in focusing and channeling resources toward priorities," said Marshall Fitz, director of immigration policy at the Center for American Progress and the author of a report on the need for deferred action. "You run into a legal authority question, or creating a constitutional crisis between the branches, if the president refuses to enforce a duly-enacted law ... but other than that, he's got extremely wide latitude to prioritize the resources Congress appropriates."

The memo from American Bridge looks back at immigration policy from the days of President Ronald Reagan through those of President George W. Bush. The instances of selective enforcement highlighted include:

The Reagan administration easing immigration standards for 200,000 Nicaraguan exiles fleeing communism in 1987. That year, Attorney General Edwin Meese instructed the U.S. Immigration and Naturalization Service to ''encourage and expedite Nicaraguan applications for work authorizations'' and ordered the service to ''encourage Nicaraguans whose claims for asylum or withholding of deportation have been denied to reapply for reopening or rehearing.''

A 1990 executive order from President George H. W. Bush making it easier for Chinese students to stay in the country should they fear persecution upon being sent back to China. The action effectively stopped deportation proceedings against these students for nearly four years.

A 1991 executive order, again from Bush, that delayed deportation of Kuwaiti residents for four years, which came following Iraq's invasion of that country.

The Clinton administration's decision in 1993 to grant an 18-month extension of a deferred action departure program affecting U.S.-based Salvadoran immigrants. The program had been launched to help those fleeing a civil war in that country.

A 2001 George W. Bush executive order that gave 150,000 Salvadorans the right to remain in the country 18 more months after their country was hit by an earthquake.

And a 2002 Bush executive order that expedited naturalization proceedings for those green card holders who had enlisted in the United States military. The order eliminated the three-year waiting period that had existed up to that point.

Critics of the president have argued that these past actions do not necessarily justify future ones of different scope. Mark Krikorian, executive director of the Center for Immigration Studies and an opponent of Obama on immigration, said nearly all past presidents issued executive orders in response to emergencies abroad, which fell under their foreign policy powers and responsibilities. Giving deferred action to millions of people would be a different matter.

"When you're giving legal status in an ad hoc fashion to five million people, that is different in kind than giving it to 80,000 Chinese illegal aliens after the crackdown in Tiananmen, or different even from the half million who got DACA," Krikorian said, referring to Obama's Deferred Action for Childhood Arrivals policy, which lets undocumented young people who came to the U.S. as children apply to stay and work.

Krikorian did acknowledge that there are not necessarily statutes banning the president from taking expanded action. But that, he added, isn't a basis for taking the action anyway.

"There's all kinds of things Congress has not explicitly prevented the president from doing because it's never occurred to them, and it's never occurred to any president," he said. "I can't come up with any examples that aren't crazy, but, you know, delivering the State of the Union address in a Donald Duck mask or something. Things that never would occur to anyone are by definition not in statute."

The American Bridge memo is meant to make the case that the idea of taking executive action to ease immigration laws has, indeed, occurred to past presidents. And while the majority of instances spotlighted in the memo were reactions to foreign crises, those weren't the only precedents available to Obama.

As Mother Jones' reported in 2012, during the George W. Bush administration, immigration adviser William Howard wrote a memo recommending the president provide leniency to the undocumented when "compelling reasons exist," such as "sympathetic humanitarian factors" or their relation to a service member.

There also is precedent for granting deferred action to a large number of unauthorized immigrants. In 1990, the commissioner of Immigration and Naturalization Service issued a policy to grant deportation relief for spouses and children of those who gained legal status through the Immigration Reform and Control Act of 1986. That policy could have applied to an estimated 1.5 million people, according to a 2012 report from the nonpartisan Congressional Resource Service. The actions Obama reportedly is considering could give deferred action to a far larger number of undocumented immigrants, but there are also more undocumented immigrants in the country in 2014 than there were in 1990.

"Given the size of the undocumented population, the scope of the executive action has increased kind of proportionately," Fitz said. "The need has increased proportionately."

Regardless of the legal ground that Obama holds, his forthcoming order almost assuredly will have immense political ripple effects. Following a summer spent debating how to respond to a wave of undocumented children showing up on the southern border, House Republicans responded with legislation to effectively deport DACA recipients and repeal the program. The president's forthcoming action likely will be a direct rebuke.

"He’s going to go for it," Frank Sharry, the founder and executive director of America’s Voice, an immigration reform group, predicted during a recent taping of the HuffPost show Drinking & Talking. "He is going to be rolling a hand grenade in the middle of American politics that is going to explode. It is going to have untold effects on the midterm. I think he is going to do it before the midterm. It is going to have a huge impact on 2016. But I actually think he is playing to history more than the immediate politics."

While advocates like Sharry may be excited at such a proposition, they are also acutely aware that the president will face heavy criticism for any action he takes. Bob Sakaniwa, the deputy director of advocacy at the American Immigration Lawyers Association, said Obama could expand deferred action under the same legal justifications he used for DACA, but acknowledged Republicans will oppose it either way.