Democrats could pursue legal fights against the reluctant witnesses, but they simply don’t have that option if they want to keep momentum for the inquiry and wrap up the impeachment process before the 2020 presidential campaign begins in earnest.

Democrats are now likely to wind down their closed-door depositions after next week. That means the public-facing part of the impeachment inquiry could begin as soon as mid-November, when the House comes back into session after a brief recess next week.

Democrats involved in the investigation say they don’t need five, six or seven witnesses to affirm the same set of facts that Trump himself has already acknowledged, or what was provided by witnesses with firsthand knowledge. In the midst of the investigation, for example, Trump publicly urged Ukraine and China to investigate Biden — which Democrats and even some Republicans knocked as an open solicitation for foreign interference in the 2020 election.

With that in mind, leads that may provide evidence of wrongdoing by officials further down the food chain have become less compelling, investigators say.