For months, congressional Democrats have looked to Robert Mueller to offer the justification for opening an impeachment inquiry against President Donald Trump for obstruction of justice. On Wednesday, the special counsel did everything but flash the green light for which they've been waiting.

Mueller's 10-minute statement was a careful and telling distillation of the 448-report he issued earlier this spring. He repeated that, had he and his team been able to clear the president of obstruction, they would have done so, but did not. He then made clear that because charging a sitting president with a crime is prohibited by Justice Department regulations, the only way to hold a sitting president accountable for possible crimes lies with Congress and powers vested by the Constitution.

Mueller's appearance now leaves House Democrats, led by Speaker Nancy Pelosi, D-Calif., with an unpalatable choice. She can authorize a politically explosive impeachment inquiry opposed by a majority of the American people - and one that surely would die in the Republican-controlled Senate - or appear to abdicate in the face of the evidence of obstruction contained in the Mueller report.

This is the choice that has been weighing on the speaker for some time, but Mueller's statement -- and his declaration that he would offer nothing more substantive than what is in the report even if called to testify on Capitol Hill -- adds significantly to the pressure to make a decision, one way or the other. Pelosi, however, appears to prefer to defer that decision as long as possible.

Nothing Mueller said Wednesday was not there in the pages of his report, but the power of his appearance -- the first time he has spoken publicly since he took charge of the investigation two years ago -- carried weight that the written word might not have.

Mueller left it to Congress to make its own decisions about impeachment, but overall he provided little comfort to the president. To the contrary, he made a series of points that undercut what Trump has claimed about the investigation and about what the investigators concluded.

The president had said repeatedly that the investigation was a "witch hunt." He has repeatedly questioned whether the Russians interfered in the 2016 election and that their efforts were aimed at helping him and hurting Hillary Clinton. He has claimed, since the report was issued, that Mueller's team found no collusion, no obstruction and therefore the report amounted to "total exoneration."

Mueller justified the investigation as a response to "multiple, systematic efforts to interfere in our election" by the Russians. That his team concluded that there was not sufficient evidence of a conspiracy by associates of the Trump campaign, he said what Russians did "deserves the attention of every single American." That presumably includes the president.

Mueller stressed that because of long-standing Justice Department regulations, charging the president was "not an option we could consider." But he specifically noted those same departmental rules say "that the Constitution requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing."

After Mueller's statement, the president issued a tweet that was a several steps removed from his previous claim of "total exoneration." "Nothing changes from the Mueller Report," he tweeted. "There was insufficient evidence and therefore, in our Country, a person is innocent. The case is closed! Thank you."

Congressional Democrats countered. The case is far from closed, they said, but exactly what path they will follow remains in question. House Judiciary Committee Chairman Jerrold Nadler, D-N.Y., speaking in New York, vowed to push forward. On the question of whether he would launch an impeachment inquiry, he said, "All options are on the table."

House Democrats cannot have it both ways indefinitely. On Wednesday, they continued to accuse the president of committing "crimes, lies" and other misdeeds, as Nadler put it during his brief news conference. Pelosi spoke in a statement of investigating the president for "his abuse of power." She added, "The American people must have the truth."

During an appearance in San Francisco, Pelosi echoed Nadler that all options are on the table, but she reiterated that she would rather move deliberately, not hastily. She said all investigations underway in six House committees will continue, that the House will continue to seek documents and testimony and will let the evidence guide the decisions.

In pointing to the various investigations, Pelosi implies that there could yet be other evidence produced that would put the president in jeopardy beyond any questions of obstruction of justice. She argued that any case against the president must be compelling -- "iron clad," as she put it - to create support for further action and possibly affirmation by the Senate. "We want to do what is right and get results," she said, emphasizing "results" as her ultimate goal.

Others are more impatient. Several Democratic presidential candidates and some House Democrats, spurred by Mueller's words, are now demanding that the House move immediately to an impeachment inquiry. But they do not yet constitute critical mass that forces Pelosi's hand. A majority of rank-and-file Democrats also favor moving toward impeachment, but House leaders are weighing the overall cost of yielding to public opinion within their own party versus the potential cost striking at the president without success.

Many Democrats still want to hear from Mueller directly. They want him to answer their questions about his investigation. But the special counsel is a by-the-book prosecutor and career Justice Department official. He conducted the investigation on his terms, with no leaks. He made his statement on Wednesday in the way he wanted, with his own words written out and no questions taken from the reporters.

If he were to eventually appear on Capitol Hill, it's doubtful House Democrats could extract from him any more than what he gave to the public on Wednesday. He said so explicitly. "The report is my testimony," he said. "I would not provide information beyond that which is already public in any appearance before Congress."

Democrats perhaps hoped Mueller would yet throw them a lifeline by stating directly that the evidence generated by his investigation justifies impeachment proceedings. On Wednesday, he signaled they won't get that from him, but suggested they have what they need and the power to act, if they choose.