Former "The Apprentice" contestant Summer Zervos filed a lawsuit against President Donald Trump, putting her in a select category of people who tried to do something virtually impossible: sue a sitting president.

But thanks to a previous case involving President Bill Clinton, she might actually have a chance to get her case heard.

Trump enters the Oval Office with dozens of lawsuits pending, both as a defendant and plaintiff.

It's possible to sue the president personally under some circumstances, but the results of previous litigation mean "that courts should think carefully about how they conduct such litigation to minimize the burden on the president's ability to discharge his duties," University of Texas law professor Stephen Vladek told Vice Magazine.

This means that any suit against Trump, even one with merit, would likely "be put on hold for some time, perhaps even the entire duration of the presidency."

Zervos was one of a group of women who accused Trump of sexual harassment, specifically for groping and kissing her during a 2007 meeting. Trump denied the allegations and called Zervos and the other accusers liars who made up their stories to damage his candidacy.

Zervos claims in her new suit that the denial amounts to defamation.

Suing a sitting president for a civil claim is rare but not unprecedented.

One of the stranger cases involved President John F. Kennedy, who was sued by Hugh Bailey, a Mississippi state senator renowned for riding a donkey.

Bailey was a passenger in a car driven by Kennedy's driver and was involved in a traffic accident during the 1960 Democratic National Convention. The crash left Bailey unable to ride said donkey, and he sued Kennedy.

Kennedy settled the case and moved on, leaving open the question of whether a president is liable for actions he took before becoming president.

Westboro Baptist Church head Fred Phelps sued President Ronald Reagan in 1984 for appointing an ambassador to the Vatican, arguing that it breached the separation between church and state. Phelps' suit was thrown out due to lack of standing.

President Barack Obama was no stranger to lawsuits.

Several suits were filed against him regarding his birth certificate. Every one was thrown out.

Ten House members also sued him, alleging that he violated the War Powers Act in connection with U.S. actions in Libya. A federal judge tossed the suit a few months later.

"I think one thing people are going to find out if they don't know already is that the Supreme Court has been remarkably successful for the last 35 years at making [it] harder for private individuals to sue the federal government," Vladeck told Vice.

The reason? Nixon v. Fitzgerald, a 1982 case that dealt with the fallout from President Richard Nixon's firing of an Air Force intelligence analyst in 1968. In a 5-4 decision, the Supreme Court ruled that the president has absolute immunity from civil actions related to his time in office.

But the Republican effort to oust Clinton in the 1990s dramatically complicates legal matters for the new Republican president.

Paula Jones sued Clinton in 1994, alleging sexual harassment while Clinton was still governor of Arkansas.

The Supreme Court ruled two years later (in Clinton v. Jones) that the absolute immunity granted by the Fitzgerald ruling didn't extent to civil suits related to pre-presidency incidents.

Clinton was deposed in the case, and his perjury during that process resulted in his impeachment in 1999.

In the short term, this was a win for Republicans.

But it might make Trump's legal problems much worse: Under Jones vs. Clinton, Trump would lose the same protections Clinton lost.

"Taking the office would not protect Mr. Trump from lawsuits that have been filed against him already or lawsuits that could be filed against him for civil matters that arose before he became president," attorney Stephen Kaufman told The Hollywood Reporter. "Having said that, there would be a mountain of logistical issues in trying to pursue a civil claim against a president."

Trump does have a variety of defense mechanisms at his disposal, including delaying, trying to get the motion dismissed, claiming that the statement was part of his "public persona" or just settling out of court. But the Jones lawsuit gives Zervos' suit the opportunity to get much further than it might have otherwise.