NEW YORK (Reuters) - John Dean entered the witness protection program. Valerie Plame feared for her children.

FILE PHOTO: Former CIA operative Valerie Plame Wilson arrives for the screening of the film "Fair Game" at the 36th American film festival in Deauville September 9, 2010. REUTERS/Vincent Kessler/File Photo

Both are veterans of U.S. political scandals that threatened the White House, and they have a warning for the witnesses who are testifying against President Donald Trump in the current public impeachment hearings. Life is about to change, it could get ugly, and death threats will become routine.

“You know that politics is a blood sport, but you can never quite be prepared for what is coming your way,” Plame, who was at the center of a 2003 episode that rocked the presidency of George W. Bush, said in a telephone interview. “They’re going to be subjected to all kinds of abuse.”

The Democratic-led U.S. House of Representatives began calling the first public witnesses in the impeachment inquiry on Wednesday, hearing from officials who handled U.S. policy in Ukraine under the Republican president. Testimony will resume on Friday and continue next week.

Previous presidential scandals have turned anonymous bureaucrats or secretive operatives into household names. Those on the wrong side of the president discovered just how much intimidation a White House can marshal, especially when backed by outside acolytes and media allies.

Trump and his supporters have already started attacking one witness due to testify, U.S. Army Lieutenant Colonel Alexander Vindman. They have also targeted the anonymous whistleblower who started the inquiry by raising questions about Trump’s July 25 telephone call with Ukrainian President Volodymyr Zelenskiy, when Trump asked Zelenskiy to investigate political rival Joe Biden.

Crossing a president, as Dean, a former White House counsel, did in Watergate and civil servant Linda Tripp did in the impeachment of former President Bill Clinton, can trigger an avalanche of hate mail.

But rallying to the president’s defense can pay dividends. When National Security Council staffer Oliver North enthusiastically testified in favor of President Ronald Reagan in the Iran-Contra affair, he became a darling of conservatives, launching a new career as media personality and political activist.

‘HOLD FAMILY CLOSE’

Plame, a former CIA covert operations officer who is running as a Democrat for a U.S. House of Representatives seat in New Mexico in next year’s election, shot to unwanted fame for her role in discrediting Bush’s justification for starting a war in Iraq.

A Bush aide disclosed to a journalist that Plame worked for the CIA, exposing her to an onslaught from the president’s supporters and forcing her to resign since her cover was blown. Plame said the ensuing firestorm lasted for years.

Her advice to the current witnesses?

“Hold their family and their true friends close, and try to understand the bigger picture. This is such an important, historic time in our country,” Plame said.

Tripp, who encouraged former White House intern Monica Lewinsky to step forward and disprove Clinton’s denials of their affair, did not respond to a Reuters request for comment. In a 2018 speech, she lamented that it was “virtually impossible to get your good name back” following attacks by Clinton allies.

“There’s nothing quite like it, and there’s nothing that can prepare you for it,” Tripp said on National Whistleblower Day, according to a Washington Post report of the address.

Dean, who was President Richard Nixon’s White House counsel, drew the ire of the president’s men by detailing the Watergate cover-up before a Senate committee and a national television audience.

That led to death threats so vicious he spent 18 months in and out of witness protection, Dean said in a telephone interview.

Dean said the Trump witnesses could avoid similar treatment if Republican leaders toned down their rhetoric, but he was pessimistic considering that some were advocating revealing the name of the whistleblower.

Given that some backlash is inevitable, Dean had one recommended course of action: “If you tell the truth, you’ve got nothing to worry about.”