But Democrats have to face it: They only get one shot. One. An impeachment that leads to acquittal by the Senate, no matter how legitimate, will be branded a failure that would be even less credible if there’s a second attempt before the election next year or should Trump be reelected, even if the alleged crimes are far more grave.

As the story explodes, and more questions are raised not just on Trump’s conduct with Ukraine but with Turkey as well, Democrats seem to think that piling up blocked subpoenas for an obstruction charge is good enough, given the polling that continues to trend against the president on the subject of impeaching him. But obstruction of Congress should be added to charges backed by evidence — facts that Trump, Republican senators and voters must face. And what Republicans know is that the bad news will just keep coming. The more the administration stonewalls, the more leaking and whistleblowing that will likely result. As Rep. Jim Himes, who serves on the House Intelligence Committee, told the New York Times, “There is another risk [in rushing to impeach], that you don’t get to the bottom of the story.”

In addition to the Ukraine story now involving Vice President Mike Pence, Secretary of State Mike Pompeo, and Energy Secretary Rick Perry, Democrats will have to examine the role of Attorney General Bill Barr. If Barr has known since February about the investigation into Giuilani’s now-charged associates, why would he have refused to open an investigation into the July 25 phone call when the Intelligence Community Inspector General referred it to the FBI as a potential campaign finance violation?