House and Senate Republicans are vociferously denouncing Sen. Chuck Schumer’s sensible request that four likely eyewitnesses to President Trump’s Ukraine actions testify in the Senate impeachment trial.

They say the request for witnesses shows the House did not do a thorough job in its impeachment inquiry. It should have obtained the testimony before voting for impeachment articles, they argue, and the Senate trial should not make up for that deficiency.

That’s nonsensical, and flies in the face of the Watergate precedent.

In Watergate, critical new evidence emerged after the House Judiciary Committee voted for articles of impeachment against Richard Nixon, despite the committee conducting an unquestionably thorough investigation. The same thing could very well happen this time — new damning evidence against Trump could emerge in the Senate trial. That’s the real reason Republicans are resisting Schumer’s request for witnesses.

In Watergate, the House Judiciary Committee received information from the Senate Watergate Committee and the Watergate grand jury (via court order). But it also subpoenaed many Nixon tape recordings, which Nixon withheld. The committee did not go to court to obtain those recordings. Instead it treated the president’s obstruction as an impeachable offense in itself, and adopted an impeachment article (Article III) against Nixon on that ground. This is exactly the procedure the House followed with its second article of impeachment against Trump, who directed his administration to disobey all subpoenas.

Then, as now, most Republicans on the House Judiciary Committee during Watergate refused to support impeachment. They made the same baseless claim Republicans parrot today: that there was no evidence of criminal conduct.

But even without the subpoenaed recordings, the 1974 Judiciary Committee had enough evidence to vote up two other articles of impeachment, one dealing with the Watergate cover-up and the other with Nixon’s abuse of power and misconduct. It was sufficient (if not overwhelming as it was for me) to convince all the committee Democrats, including three Southern Democrats representing very pro-Nixon districts and seven Republicans, to vote for the articles of impeachment.

Then, just days after the committee voted, explosive new evidence against Nixon came to light. In a case brought by the Watergate special prosecutor against Nixon, the Supreme Court ordered Nixon to release certain tape recordings, including the so-called “smoking gun” tape, on which Nixon is heard ordering his chief of staff to obstruct the FBI investigation.

At that point, House Judiciary Committee Republican holdouts announced they would vote for impeachment, and Nixon’s fate was sealed. He resigned rather than face certain impeachment and conviction. It would have been absurd to blame the committee for not obtaining the tape before voting for articles of impeachment. Nixon withheld them. But regardless of when in the process it was obtained, the tape, the evidence itself, is what counted.

It’s quite possible that the witnesses Schumer requested have “smoking gun” evidence against Trump. John Bolton, the ex-national security adviser, and Mick Mulvaney, Trump’s acting chief of staff, seem to have had personal interactions with Trump regarding withholding military aid and a White House meeting to bully Ukraine’s president into announcing politically motivated investigations. Trump’s unprecedented steps to silence these witnesses strongly suggest their testimony could be harmful to him

Suppose the Senate refuses to call witnesses, acquits Trump, and then evidence emerges showing he was guilty as charged? It would be an indelible blot against the Senate Republicans and our democracy, and the Senate has a duty to prevent it. Alternatively, suppose the information the witnesses have turns out to be exculpatory. That would be all the more reason for the Senate to seek it.

Our democracy survived the “smoking gun” revelations about Nixon and Gerald Ford’s ascendancy to the White House. It would survive if new evidence is presented a proper Senate trial, even if it means Trump is removed and Vice President Mike Pence takes over. But will it survive if the Republican-controlled Senate violates its special oath to do “impartial justice” in the trial, if it perpetuates a cover-up, and puts party above country when the integrity of our elections is at stake? If the Senate fails to uphold the rule of law, our democracy’s foundations will be shaken. Watergate showed how critical evidence can emerge at any point in impeachment proceedings. It would be outrageous to ignore that lesson.

Elizabeth Holtzman represented Brooklyn for four terms and was a member of the House Judiciary Committee that approved articles of impeachment against Richard Nixon.