(CNN) This week is arguably the most important to date in the impeachment inquiry into President Donald Trump. It's the first time there will be public testimony, which comes at a time when the American people have become seemingly locked in their impeachment positions: They're for the inquiry but much less sold on impeaching and removing Trump from office.

The inquiry has not recently produced major movement toward Americans wanting to impeach the President. Over the last month (the middle of October to the middle of November), 47% of Americans have said they are for impeaching and removing Trump in the average poll . That's nearly equal to the 44% who are against it. These numbers are the same as an average of polls taken before this point but after the inquiry was announced in late September.

Past impeachment timelines for Bill Clinton and Richard Nixon offer two very different possibilities on where we go from here. From the start, Americans were against impeaching and removing Clinton from office during the 1998-1999 inquiry, and they remained that way.

But the case against Nixon during 1973 and 1974 should give Democrats more optimism. Opinions on impeaching and removing Nixon from office remained stagnant for months on end. Americans were split on the question in Harris polling from January 1974 to April 1974 for Nixon, just like they are now for Trump.

Then the dam started to burst. A combination of factors, including Nixon's refusal to turn over any more materials in the Watergate case and public hearings during the House impeachment investigation in May 1974 , began to change the tide of public opinion.

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