I don't know if Pelosi is right, but history seems to argue in her favor. Via USAToday, Pelosi responds to her critics:

FERGUSON, Mo. – House Speaker Nancy Pelosi dismissed fellow Democrats who say she has set the bar too high for impeachment of President Donald Trump.

In an exclusive interview with USA TODAY, Pelosi said some House progressives have "wanted to impeach the president since the day he got elected."

"You're wasting your time, unless the evidence is so conclusive that the Republicans will understand," Pelosi, D-Calif., told USA TODAY. "Otherwise, it's a gift to the president. We take our eye off the ball."

The speaker said, instead of impeachment, Democrats needed to stay united in pushing through legislation that they campaigned on, such as addressing rising health-care costs and creating jobs.

Pelosi told The Washington Post last week Trump was "just not worth it."

Many progressives saw this as Pelosi as giving a pass to the president.