Julian Zelizer is a professor of history and public affairs at Princeton University and author, with Kevin Kruse, of the new book " Fault Lines: A History of the United States Since 1974 ." Follow him on Twitter at @julianzelizer . The opinions expressed in this commentary are his own. View more opinion articles on CNN.

(CNN) Sen. Elizabeth Warren was the first 2020 Democratic candidate to call for impeachment proceedings to begin against President Donald Trump. In a tweet on Friday, she said, "To ignore a President's repeated efforts to obstruct an investigation into his own disloyal behavior would inflict great and lasting damage on this country, and it would suggest that both the current and future Presidents would be free to abuse their power in similar ways."

Many other Democrats, however, are fearful of going down this path. With the 2020 election around the corner, they worry that moving forward with impeachment will stimulate a political backlash against the party and hurt the Democrats' prospects of winning back control of the White House.

But Democrats can't afford to be so fearful about impeachment proceedings. And it might very well be that the Mueller report has forced their hand. While the first part of the report points to highly unethical and problematic behavior by the Trump campaign, the second section lays out some strong evidence of the President's continued efforts to interfere with the Mueller investigation. And this is in addition to his overt efforts to undermine Mueller, most notably from his bully pulpit of choice -- Twitter

Of course, Democrats have reason to be wary. It didn't go particularly well for Republicans in 1998, when the House, led by Newt Gingrich, impeached President Bill Clinton for lying under oath and obstructing justice into the investigation of his affair with Monica Lewinsky. In fact, Clinton's approval rating soared to 73% following the GOP-led impeachment. And the House Republican majority shrunk that year

But the substance of the current impeachment debate is quite different. In the case of Clinton, a large portion of America saw the investigation as revolving around the private life of the President. But, in the case of Trump, this was an investigation into contacts between Trump campaign officials and individuals connected to a Russian government who were attempting to interfere in the 2016 US election -- as well as the President's ongoing efforts to stop the investigation. There is simply no comparison in the weight of the underlying charges.

Public opinion has reflected that a majority or close to a majority of the public has continued to approve of Mueller, despite the constant attacks from the President. Meanwhile, Trump has yet to win a majority of American voter support in his first two years in office. It would seem, then, that the public agrees that the substance of the charges is serious, and the content of the Mueller report only intensifies the severity of what the President has done while in office.

What Democrats do regarding impeachment proceedings will also say a great deal about the party's views of presidential power. The issue is not, and has never been, what is the best way to remove Trump from the White House. The question has been whether Democrats take the abuse of presidential power seriously and whether they insist that the commander in chief needs to live under some restraints. If Congress allows the actions that Mueller documented in the obstruction portion of the report to stand, they will help to establish a dangerous precedent for future inhabitants of the Oval Office. In contrast, launching impeachment proceedings would be a strong act that formally puts the party on record as not accepting these actions as legitimate and believing that they are severe enough to warrant consideration of impeachment.

Importantly, impeachment proceedings are not the same as impeaching a president. The House would have to pass a resolution referring the case to the House Judiciary Committee or a select committee. The committee would conduct its own hearing, with a staff investigation of the evidence, to decide whether the grounds exist for voting on articles of impeachment.

If those grounds exist, the committee must pass each article by a majority vote -- at which point they would be sent to the floor for a vote. If the House votes in favor of any article by majority vote, only then does the case reach the Senate, where the bar is much higher, requiring two-thirds support to convict.

Democrats who fear a backlash to moving forward with the impeachment process might want to consider the political consequence of being a party that decides to let this abuse of power stand. At the most basic level, doing nothing will allow Trump to spin his narrative that the entire issue was a partisan hit job.

And political parties can be rewarded for doing the right thing. The entire Watergate saga made this clear. After a brutal multi-year investigation into President Richard Nixon that shocked the nation and resulted in his resignation, Democrats retained control of the House and Senate in the 1976 election -- building on their sizable majorities in the 1974 midterms -- and won the presidency. President Jimmy Carter capitalized on public anger about presidential wrongdoing and succeeded as the candidate who best responded to the distrust that existed about our leaders.

It is also worth noting that even with the controversial and unpopular impeachment proceedings in 1998, Republicans actually didn't lose all of their power. The GOP retained control of Congress (temporarily losing a split Senate when Jim Jeffords caucused with Democrats in 2001, though they regained control in 2002). And George W. Bush won the presidency and served for two terms. While most Democrats don't want to make Clinton's impeachment the baseline as they consider what to do next, they should understand that Republicans did not totally fall apart after moving forward with proceedings on a much more questionable charge than the President is currently looking at today.

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For Democrats who insist on gaming out what this will all look like, they should also consider the possibility that by refusing to hold the President accountable, they could end up improving his chances for re-election and giving legitimacy to his use of power. By doing nothing, one can imagine the Democrats helping Republicans elevate the "witch hunt" narrative and diminishing the serious political problems this administration already faces for its behavior.

Focusing on the economy, Trump could put together the coalition that brought him to office in 2016. Once that second term begins, the behavior documented in the Mueller report and elsewhere would have an electoral stamp of approval.

When the Mueller investigation started, the report shows, Trump was convinced that his presidency was "f--ked." But he underestimated the partisan loyalty that he could count on from the GOP. And he might also have underestimated just how politically trepidatious the opposition party had become.