When John Dean testified in June 1973 before the Senate Select Committee on Presidential Campaign Activities — for a full week — the nation was riveted. Here was a young former counsel to the president, telling the country that he had warned Richard Nixon that “there was a cancer growing on the presidency” and that “if the cancer was not removed, the president himself would be killed by it.” All three major networks carried his testimony. But for all the drama of Dean’s appearance, it did not push the public to conclude that Nixon had to go.

The Watergate hearings captured a huge TV audience — 80 percent of Americans tuned in, by some estimates — and began the process of corroding Nixon’s credibility. But for months after Dean spoke, public opinion, while deeply critical of Nixon, remained opposed to his impeachment and removal from office. It took a year of further revelations, culminating in the court-ordered release of a tape on which Nixon was heard ordering his chief of staff to tell the CIA to kill the FBI’s Watergate investigation, to push public opinion solidly toward impeachment.

Democrats hope that the public hearings that began this past week will end with voters — including a substantial number of Republicans — concluding that Trump deserves removal. But there are reasons for skepticism. What we have today is Watergate in reverse: The “smoking gun” has already been produced, in the form of the rough transcript of President Trump’s July 25 conversation with Ukrainian President Volodymyr Zelensky. Witnesses subsequently corroborated the administration’s efforts to pressure Ukraine to dig up dirt on former vice president Joe Biden. In short, the TV hearings are coming at the end of a substantial investigative process, not the beginning. That difference, combined with the deeper polarization of American politics and media, makes it unlikely, barring a true bombshell, that the hearings will significantly move public opinion.

To be sure, Nixon had further to fall than Trump does. He entered his second term in a far stronger position than Trump entered his first: Nixon won every state except Massachusetts and boasted an impressive 62 percent approval rating in November 1972, according to Gallup. The Watergate break-in had happened in June 1972, but, although The Washington Post’s Bob Woodward and Carl Bernstein wrote relentlessly about the scandal, Americans were largely unmoved. They were focused on ending the war in Vietnam “with honor,” a pledge Nixon made in his campaign that year.

Although the timeline gets compressed in our collective memory, the “drip, drip, drip” of revelations about Watergate came over a full two years. The trial of the Watergate burglars arrived in January 1973 — the same month the United States reached a settlement with Vietnam, in Paris (which caused Nixon’s approval rating to hit 67 percent). The trial left U.S. District Judge John Sirica and many others wondering if higher-ups were being protected. In early February, the Senate voted unanimously to investigate campaign activities from the 1972 election.

In April, Nixon accepted the resignations of two of his top advisers and his attorney general, and he fired his White House counsel, Dean. Then came Dean’s testimony, a genuine spectacle (attended by John Lennon and Yoko Ono). That hearing was detailed and shocking, but no one came forward to corroborate Dean’s story. Unlike in the case of the Ukraine whistleblower, it was his word against the president and all his men.

Dean, however, had included in his 60,000-word written statement his suspicion that he had been taped in one meeting with Nixon. He had no idea there was a vast taping system in place; few did. But Alexander Butterfield, a presidential aide, confirmed the existence of the system two weeks later, and the fight for the tapes was on.

Dean’s testimony was not the turning point some recall. While Nixon’s approval rating fell to 31 percent by early August, only 26 percent of Americans thought the president should be impeached and forced to resign; a hefty 61 percent were still opposed. In October, the battle for the tapes came to a head. The president ordered his attorney general, Elliot Richardson, to fire Watergate special prosecutor Archibald Cox after Cox refused a compromise over the production of the tapes. Richardson declined and resigned, as did his deputy, leaving the solicitor general, Robert Bork, to carry out the president’s directive.

For the first time, calls for Nixon’s impeachment resounded in Congress. (And within weeks, Nixon’s lawyers had to admit that there was a significant gap in one of the few tapes provided to Sirica.) Then in March 1974, as the House considered impeachment, a grand jury indicted seven top administration officials, including former attorney general John Mitchell. Even at this point, however, backing for impeachment hovered stubbornly at 38 percent. The fatal blow came at the end of July 1974 — a full year after Dean testified, and two years after the break-in — when the Supreme Court ordered Nixon to turn over his tapes. The “smoking gun tape” made the difference. Finally, public opinion polls showed that a majority of Americans, 57 percent, favored impeachment and removal. Nixon resigned about two weeks later.

Contrast that extended narrative with the current situation. The whistleblower has already brought to light what by any measure should be considered a “smoking gun” transcript. Private testimony — and now, public testimony — by multiple officials has added firsthand accounts of Trump’s conversation with his Ukrainian counterpart. They have also added details about the actions of the president’s personal lawyer, Rudolph Giuliani; the U.S. ambassador to the European Union, Gordon Sondland; and others in an “irregular” diplomatic channel to further the president’s private political agenda. The hearings appear likely to flesh out a narrative that is already widely known.

The fact is that the public knows what Trump did, and many voters think it was wrong. But Trump supporters, at least so far, simply don’t care — even with the attempt to solicit foreign interference in U.S. elections all but confirmed. (Just before the public hearings, 94 percent of Republicans opposed impeachment, although a small majority of voters, 51 percent, supported it; Republican support will be necessary to change minds in the Senate.) And unlike in the 1970s, the public is now consuming its impeachment news through highly partisan outlets, so fewer people are having their assumptions challenged.

The lesson from the Watergate TV hearings is that public reaction to presidential scandals tends to be measured; it takes repeated body blows to weaken a president’s credibility to the point that impeachment becomes acceptable to a significant majority. Given that the House expects to vote on impeachment before the end of this year, with a Senate trial in the first quarter of next year, there’s limited time for new or additional revelations to emerge that would shock the nation into the conviction that removal is necessary. In which case public opinion will remain much as it is; the House will impeach; and the Senate will not convict. Trump and many of the politicians who supported him will then face the voters in the fall.

The public is rightly interested in Watergate parallels today, but right now it’s the differences between the two sets of hearings that are the most striking.

Twitter: @jimrobenalt