Why haven’t efforts to impeach President Trump gained Watergate-style momentum? The lack of energy has created a sense of bafflement and disappointment among some of the president’s most determined adversaries. But there are some simple reasons for it. Here are three:

1) The facts are different. In Watergate, the underlying crime was a break-in at Democratic National Committee headquarters, perpetrated by burglars paid by President Nixon’s re-election campaign. The scandal proceeded from there. In Trump-Russia, the underlying crime was the hacking of the DNC’s and John Podesta’s emails — a crime committed by Russians in Russia. Special counsel Robert Mueller, who indicted a number of Russians and Russian entities for their actions, spent two years trying to find conspiracy or coordination between the Russians and the Trump campaign. He failed.

That single fact has shaped every other aspect of the Trump-Russia affair. In Watergate, the cover-up flowed from Nixon’s desire to conceal his campaign’s involvement in the break-in and other political dark acts. It formed the bulk of the obstruction of justice case against Nixon, which in turn served as the basis for articles of impeachment. In Trump-Russia, Mueller did not charge, although he clearly suggested, that Trump obstructed the investigation of an event — conspiracy/coordination — that did not happen.