Even President Donald Trump, according to a CNN source, now fears that impeachment is a "real possibility."

But many Democrats are now worried that if they move forward with impeachment proceedings, led by incoming chairman of the House Judiciary Committee, Jerry Nadler, the decision will inevitably backfire on their party. The investigation, skeptics warn, will produce an instant backlash. Democrats will appear to be reckless partisans, seeking to undertake a coup. Every gain that has been made in the midterm will disappear.

The Democratic fears likely stem from the memories of the 1990s, when the effort by Speaker Newt Gingrich and the House Republicans to impeach President Bill Clinton for perjury and obstruction of justice turned into their political nightmare. Public opinion turned against the GOP and Clinton ended his term with high and steady approval ratings.

It is reasonable for Democrats to worry that history might be repeated. 

Yet sometimes impeachment proceedings are warranted. If the findings of Robert Mueller's final report are as bad as some suspect, based on recent court filings and guilty pleas, any impeachment proceedings initiated in the aftermath could broaden, rather than narrow, opposition against the President.

This was the case when the House Judiciary Committee, under the chairmanship of Congressman Peter Rodino, impeached Richard Nixon in 1974. ...