Before a backdrop of an impeachment trial that’ll probably lack witnesses and any evidentiary documents thanks to Senate Republicans, Sen. Elizabeth Warren (D-MA) is promising to hold President Trump and his administration accountable — even if the justice is retroactive.

One of her campaign proposals, published Tuesday, would establish a Justice Department Task Force to “investigate corruption” within the Trump administration, and to “pursue any substantiated criminal and civil violations.”

It wouldn’t be the first time a new president is called on to demand answers from the last.

When President Barack Obama took office, he faced extreme pressure from certain corners to hold his predecessor accountable.

President George W. Bush left office with an abysmal 22 percent approval rate. He was weighed down with scandals concerning mass surveillance, torture programs and war profiteering. Human rights groups and liberals alike clamored for justice, especially for gruesome reports of brutality, sometimes ending in death, perpetrated on prisoners suspected of terrorism.

Obama, fresh off a hope and change campaign, brushed them off, telling ABC News that he held “a belief that we need to look forward as opposed to looking backwards.” Half-hearted investigations resulted in no charges, and the Obama administration blocked detainees’ lawsuits by invoking the state secrets doctrine.

According to Paul Pelletier, former federal prosecutor in Obama’s Department of Justice, the difference between the politicians’ approaches lies in the roots of any alleged crimes.

“These alleged crimes are financial and have nothing to do with politics,” he told TPM. “Using government contracts unlawfully is something we always go after, so from that perspective, I think it’s completely different than what Obama administration was faced with.”

The Warren campaign cited alleged wrongdoing by Commerce Secretary Wilbur Ross owning stocks influenced by administration decisions, Trump’s children enriching themselves from his business while serving in the administration and Trump’s own impeachment over the Ukraine pressure campaign.

“You have to be very, very careful if you’re merely looking at if someone did something wrong politically,” Pelletier added. “But what you’re saying is that people enriched themselves, that they used the political process to unlawfully or unfairly gain wealth…if it’s rooted in corruption you’re on much safer ground.”

Back in 2008, Obama’s forward-looking focus set the tone for the administration. Then-Attorney General Eric Holder opened an investigation in 2009 into the CIA’s investigatory methods. He ultimately closed the case, after reviewing the cases of more than 100 prisoners, without pressing any charges. In 2010, the Justice Department said there’d be no charges pertaining to the CIA destroying videotapes of the investigations. The DOJ also blocked lawsuits from former detainees, citing the state secrets doctrine.

Barbara McQuade, a U.S. attorney under Obama, told TPM that the Obama administration didn’t press charges because of the “investigation into the facts” and not because of any “blanket policy decision.”

But Pelletier said that, while the discussions would have been out of his realm as a white collar prosecutor, “of course” a consideration of precedent would have played into the administration’s decision not to go after the Bush administration officials.

Though Warren cites specific examples of corruption-flavored behavior in her proposal, it’s not hard to picture a future president, embittered by some criticism from his or her predecessor, using that power to exact revenge.

In an apparent attempt to curtail that possibility, a Warren campaign aide emphasized to TPM the limits in scope of the task force.

“The plan calls for a DOJ task force with independent authority and a limited scope to look at specific current laws that were broken: Federal bribery laws, insider trading laws, and other anti-corruption and public integrity laws,” the aide said. “It will investigate independently and prosecute or not prosecute as they see fit.”

The aide added that the proposal is not about “political rivals” but “restoring the rule of law.

“The best way to turn the page on Trump-era corruption is for people who broke the law to be held accountable so that future officials — including in a Warren Administration — will know that violating the public trust and breaking anti-corruption and public integrity laws will come with consequences.”