Democratic presidential candidates rushed Wednesday morning to call for President Donald Trump to be impeached, after Special Counsel Robert Mueller left the door open for Congress to accuse the president of obstruction of justice.

Mueller said nothing new, other than defending Attorney General William Barr as having acted in “good faith” in his summary of the investigation’s report. He reiterated that there was “insufficient evidence” to substantiate claims of Russian collusion, and said the investigation did not reach a conclusion on obstruction: “As set forth in our report, after that investigation, if we had confidence that the President clearly did not commit a crime, we would have said that.”

All of that had been said before. Yet Democrats seized on it — as well as on Mueller’s acknowledgment that he could not have charged a sitting president with a crime, as per Department of Justice policy — to demand impeachment.

Speaker of the House Nancy Pelosi — who would need to agree to bring an impeachment vote to the floor — attempted to sidestep the issue. Yet she is under pressure from inside her caucus, many of whose members spoke out Wednesday:

The demands for impeachment drowned out discussion of other policy issues. Former Rep. Beto O’Rourke (D-TX), for example, desperate to revive his campaign, launched a new immigration policy Wednesday — and was largely ignored.

That could be the pattern for the next 18 months. By holding out the possibility of impeachment, Mueller has given Democrats a temptation they cannot refuse.

That was probably not his intention. Mueller did not have to pursue an obstruction investigation, nor did he have to disclose the results of that investigation. He pointed out Wednesday that he could not indict a sitting president, but failed to note that it was also impossible to charge a retired president with obstruction of justice, for actions taken furtherance of his constitutional duties. Mueller seemed, all along, to be seeking a way to bring down the president.

The main reason Mueller declined to testify before Congress may have been that he would have faced very difficult questions about whether he had investigated the origins of the surveillance of the Trump campaign, and whether that had been linked to misinformation fed by Russia to the FBI, via former British spy Christopher Steele, the Fusion GPS opposition research firm, the Hillary Clinton campaign, and the Democratic National Committee. (If not, why not?)

Regardless — whether Democrats impeach Trump or not, they will be consumed by the issue through 2020, while Trump discusses the economy, his foreign policy successes, and his new proposals on health care and immigration.

Mueller may have hoped to hurt Trump. Instead, he gave him a huge gift.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.