Watergate made Richard Nixon the only U.S. president forced to resign. On Wednesday, ex-intelligence chief James Clapper said that scandal "pales" in comparison to the one involving Russian interference in the 2016 election.

It's impossible to know whether this scandal will force President Donald Trump from office prematurely. But it is possible, after fresh testimony from key government figures, to compare some of the new evidence with what drove Nixon from office.

The 1972 Watergate break-in triggered two years of investigations by the media, Congress and a special prosecutor. For most of that time, Nixon retained support among fellow Republicans.

But that changed after the Supreme Court rejected Nixon's claim of executive privilege and ordered him to surrender tape recordings of Oval Office conversations on June 23, 1972. On Aug. 5, 1974, the White House released them.

The tapes showed Nixon directing his chief of staff to halt the FBI investigation of the Watergate break-in. They agreed to do so through CIA officials, who would tell the FBI chief the probe could harm national security.

"They should call the FBI in and say … 'Don't go any further in this case,' period," Nixon said.



That "smoking gun" tape, documenting his personal involvement in a cover-up, destroyed his Republican support. He announced his resignation three days later.

There are no known tapes of Trump's conversations, although the president has hinted at the possibility. But fired FBI Director James Comey, in prepared testimony for his appearance Thursday before the Senate Intelligence Committee, quotes from his contemporaneous notes about them.

Comey detailed encounters in which the president expressed concern about the FBI probe of Trump campaign associates and Russian interference in the election. At a "strange" White House dinner on Jan. 27, Comey wrote, the president asked if he wanted to remain at the FBI even though he had twice earlier told Trump he did.

"My instincts told me that the one-on-one setting, and the pretense of that this was our first discussion of my position, meant the dinner was, at least in part, an effort to have me ask for my job and create some sort of patronage relationship," Comey wrote.

After Comey invoked the importance of FBI independence, he recalled, the president said, "I need loyalty."

On Feb. 14, Comey said, the president instructed other officials to leave an Oval Office meeting so they could be alone.

"I want to talk about Mike Flynn," Comey quoted Trump as saying about FBI's interest in his former national security adviser's dealings with Russian officials. "I hope you can see your way clear to letting this go, to letting Flynn go."

Comey wrote that he didn't tell FBI investigators of the request so as "not to infect" their work, and later asked Attorney General Jeff Sessions "to prevent any future direct communication between the president and me."

On March 30, he said, the president requested that Comey "lift the cloud" over his administration and disclose publicly that Trump was not under investigation. On April 11, he said, Trump called to follow up, noting: "I've been very loyal to you."

In May, Trump fired him.

Comey's testimony calls the president's conduct "inappropriate." And he describes a more direct request to curb an FBI investigation than ever emerged about Nixon.

He does not, however, assert that any of this represents criminal obstruction of justice – a legal question turning on Trump's intent, among other factors. The president has publicly denied attempting to stop the investigation.

But political reaction turns on how disclosures appear to the public and their representatives.

Even as he released those damning recordings, Nixon maintained he "insisted on a full investigation" once he had "all the facts." It didn't help. Republican leaders refused to keep defending him against an impeachment drive led by Democrats.

Trump's Republican support has remained strong. But Senate testimony on Wednesday from two other senior national security officials added new strains.

Before the same committee Comey will face on Thursday, Director of National Intelligence Dan Coats and Director of the National Security Agency Adm. Mike Rogers offered carefully worded responses to news reports that Trump sought their help in tamping down the investigation.

Coats said he hadn't been "pressured"; Rogers said he hadn't been "directed." Neither would say whether Trump had asked them for help, saying the White House might yet assert executive privilege over their conversations.

In one sign of Republican impatience, Sen. John McCain called their refusal to answer "Orwellian." In another, Intelligence Chairman Richard Burr said he expected answers in a closed session, if not publicly.

Public opinion will shape how Congress reacts to the evidence. In a Quinnipiac Poll on Wednesday, just 34 percent of Americans approved of Trump's job performance; 60 percent, including 1 in 5 Republicans, said the president had acted illegally or unethically involving Russia.

Asked whether they think Trump will serve his entire four-year term, 54 percent responded yes, 40 percent no.