Last week’s decision by Sen. Lamar Alexander (R-Tenn.) to vote against calling witnesses in President Trump’s impeachment trial, which sealed Trump’s acquittal, will have his mentor, Howard Baker, turning in his grave. Baker was the ranking Republican on the Senate Watergate Committee who famously asked, “What did the president know, and when did he know it?”

In his opening statement to the committee in May 1973, Baker pledged to conduct a “bipartisan search for the unvarnished truth. … We will inquire into every fact and follow every lead, unrestrained by any fear of where that lead might ultimately take us.” This is decidedly not the road taken by Alexander and his Republican colleagues today.

Lead House impeachment manager Adam B. Schiff (D-Calif.) closed the impeachment hearings by invoking parallels with Watergate and concluding that “far more serious than a third-rate burglary of the Democratic headquarters” is the “withholding of military aid to an ally at war. … The difference between then and now is not the difference between Nixon and Trump. It’s the difference between that Congress and this one. … Where is Howard Baker?” he asked. “Where are the people who are willing to go beyond their party to look to their duty?”

The partisan vote to block witnesses and new evidence — and Wednesday’s almost certain acquittal of Trump — confirmed Schiff’s worst fears that there is no Howard Baker in the Senate, and without Baker, the Senate Watergate hearings might have been similarly curtailed and history rewritten.

Baker was integral to the Senate Watergate investigation, according to Rufus Edmisten, the committee’s deputy chief counsel. Without him, Republicans “could have stopped it … by using procedures, by thwarting the committee system.”

When Baker was appointed to the committee in February 1973, he feared that Watergate was a partisan witch hunt, designed to embarrass an innocent president and “put a different face on a bad defeat” in the 1972 election.

President Richard Nixon was riding high in the polls, but Watergate was a looming threat.

Nixon aide John Ehrlichman told the president that his campaign chief, John Mitchell, and Mitchell’s deputy, Jeb Magruder, had perjured themselves during the trial of the Watergate burglars, but he was confident that the administration could survive the Senate hearings if officials “cut their losses” and tried to “shore up Howard Baker.”

Some historians have speculated that Baker was secretly conspiring with the White House during Watergate, thanks to Bob Woodward’s reporting that his source Deep Throat had told him that White House counsel John Dean had talked with Baker, and “Baker is in the bag completely, reporting back directly to the White House.”

But Dean denies the story, and in a previously unpublished oral history, Baker’s chief aide (who died in 2009) dismissed it as well.

Baker did meet secretly with Nixon on Feb. 22, 1973, and assured the president that he would protect his rights and that he didn’t want the Senate investigation to turn into “a fishing expedition.”

Unaware of Nixon’s role in the coverup, Baker urged the president to call in whoever was involved, find out the facts, and let Baker come clean about White House involvement in the press and “win it” for him. While Nixon might take a temporary hit politically, the problem would be solved.

In a 2005 interview, Baker also recalled urging Nixon not to use executive privilege to block his staff from testifying: “You ought to … send your witnesses up there, pounding on the door to testify. If they can’t tell your story better than a … secondary witness you’re in real trouble.”

For Baker, the defining moment of Watergate came when he asked the president about their friend John Mitchell, and Nixon replied that Mitchell might have some problems. “A lightbulb went off in my head,” Baker recalled, “and I decided, ‘You know Baker, you don’t know as much about this situation as you think you do, and you’d better just put your head down and charge into this thing and let the facts fall where they will’ … notwithstanding my personal friendship with Nixon.”

According to Baker’s chief aide, Hugh Branson, after the meeting, Baker got the feeling that Nixon didn’t know the full story and didn’t want to “clean house” because he “feared that John Mitchell was going to be implicated.” Nixon admitted to Dean that Baker’s idea of “a big slambang thing for a week … bring all the big shots up right away” was a good strategy, but he couldn’t allow three of his chief assistants to be cross-examined under the television lights “like criminals” in a “media circus.”

By failing to follow Baker’s advice, Nixon missed his chance to come clean and contain the crisis. While he believed that Baker would stay loyal and “make it appear … the hearings are honest and the administration’s cooperating,” he soon realized he was mistaken.

Three weeks later, Nixon announced that no member of White House staff would appear before the committee, claiming executive privilege. When Baker expressed surprise on television, Nixon called him a “liar … trying to be a hero” and threatened to destroy him. Nonetheless, through Branson, Baker continued to urge Nixon to reconsider to limit damage to himself and his party.

In mid-April, Nixon finally relented, but when the Senate hearings began a month later, he was furious at Baker for his “softball” questioning of Dean, who had turned whistleblower, and again on July 12 for Baker’s “manhandling” of campaign chief Mitchell. He branded the senator’s cross-examination of Mitchell “despicable” and “unforgivable … to treat him like a common criminal was inexcusable.”

Nixon had rejected a request for White House documents and told Henry Kissinger that he’d “burn every Godd---ed paper in this house … before I turn them over to that committee.”

The next day, it was Baker’s deputy counsel whose questioning of White House aide Alexander Butterfield revealed the existence of the White House taping system, giving Baker, in the words of his biographer, “a foolproof method of determining what the president knew and when he knew it.”

Nixon refused to cooperate with a subpoena for White House tapes and documents, claiming executive privilege, and a year-long court battle ensued. Crucially, unlike today’s Republicans, Baker called Nixon’s failure to make a full public disclosure either “another in an unbroken chain of bad decisions” or an indication that he had something to hide.

According to his biographer, Baker was concerned by Nixon’s willingness to pay hush money to the burglars but not yet “convinced that the high standard … [of] proof” required for impeachment had been met — until Aug. 5, 1974, when Nixon released a transcript of the “smoking gun” tape that revealed his attempt to use the CIA to block the FBI’s Watergate investigation six days after the break-in. It led to his resignation.

Three years later, Senate Watergate Committee Chairman Sam Ervin wrote a letter to Baker, professing himself “eternally grateful” for Baker’s help and recalling proudly how the impartiality of the committee silenced early cries of a “partisan witch-hunt” and “convinced the public that [Baker was] willing to go wherever the truth led.” While they had differing opinions, they were able to present a united front in public.

Ervin acknowledged that investigating Watergate was “highly unpleasant” for Baker as “a dedicated Republican,” but noted that Baker “performed in the highest degree the obligation imposed upon [him] … to seek the truth, no matter where it led and no matter whom it implicated. In so doing, you performed your duty to your country without fear or favor.”

Baker’s courage and independence to challenge the president to do the right thing, against his own party’s interests, is notably absent today. While Baker wasn’t sure until late that Nixon had committed acts that warranted removal, he kept pressing for evidence and worked in a bipartisan fashion to acquire it, despite his friendship with Nixon and every partisan reason not to.

Back in 1973, Baker invited Lamar Alexander to join his Watergate committee staff, but Alexander had worked in the Nixon White House and didn’t want to investigate his former colleagues. Now, he and his fellow Republicans have refused to hear witnesses or more evidence of presidential wrongdoing, and are planning to vote to acquit Trump. Their unwillingness to follow Baker’s lead shows how toxic our politics have become and how Republicans are more interested in protecting the president than seeking the truth.