Were it up to Senate Minority Leader Charles E. Schumer (D-N.Y.), historians would mention President Trump’s all-but-certain impeachment acquittal much the same way baseball fans mention Barry Bonds’s career home-run record — an achievement destined to be obscured by an eternal cloud.

While Trump, unlike Bonds, does not stand accused of benefiting from performance-enhancing drugs, Democrats started this week to make an aggressive case that the Republican-led Senate’s decision Friday to end Trump’s trial without summoning witnesses or documents should cast grave doubt on its outcome.

The charge has been led by the most senior Democratic officials as it grew increasingly clear this week that Republican senators would vote to reject additional evidence and pave the way for a largely partisan verdict.

Hours before the Senate voted Friday, Schumer declared any acquittal at such a trial to be “meaningless.”

“If there are no witnesses, no documents in this trial, there will be a permanent asterisk next to the acquittal of President Trump written in permanent ink,” he said, harking to the punctuation mark that once accompanied contested records in sports almanacs.

On Thursday, House Speaker Nancy Pelosi (D-Calif.) declared flatly that Trump “will not be acquitted” regardless of the vote.

“You cannot be acquitted if you don’t have a trial,” she said. “And you don’t have a trial if you don’t have witnesses and documentation.”

Prior to Trump’s trial, the Senate has held 15 impeachment trials, including two for a president. All had witnesses.

The Democratic rhetoric was, on one hand, an early attempt to salvage what promises to be a crushing political loss. After warning for months about the dangers of a partisan impeachment, Pelosi led the House down that path after allegations of grave misdeeds emerged from the Trump administration — only to find the GOP ever-willing to stand by Trump in the face of damaging revelations.

On the other hand, Schumer, Pelosi and other Democrats are launching an appeal that they hope will have staying power. In the short term, that means impressing on voters that they ought to treat Trump’s certain claims of vindication with deep skepticism. In the longer term, they are banking that history will remember unkindly those who stood with Trump.

“This is only the third time we’ve had a vote on convicting and removing a president,” said Sen. Debbie Stabenow (D-Mich.). “I think it’s going to be remembered as something incredibly serious, and certainly we want to point out to colleagues that they should be thinking about that now.”

Some Republican senators have suggested they are indeed thinking about their place in history. Sen. Lamar Alexander (R-Tenn.) launched his political career in the shadow of fellow Tennessee Republican Howard Baker Jr., who as a member of the Senate Watergate Committee helped expose President Richard M. Nixon’s wrongdoing and later persuaded him to resign rather than face impeachment.

Alexander told reporters Friday he believed he had followed Baker’s example, concluding that Trump’s “inappropriate conduct” was not worthy of removal from office nine months before an election.

Sen. Lisa Murkowski (R-Alaska) reached for institutional concerns Friday in announcing her decision not to pursue additional evidence, decrying the “partisan nature” of the impeachment and attempts to “drag the Supreme Court into the fray,” citing attacks on Chief Justice John G. Roberts Jr.

For most Republicans, any attempts to cast aspersions on the trial in the GOP Senate were met with attacks on the impeachment process in the Democratic House, which raced over the course of three months to assemble a case against Trump despite the White House blocking witnesses and withholding documents. In the end, no Republicans voted for the two articles of impeachment; Rep. Justin Amash (I-Mich.), a former Republican, joined with Democrats.

“There is a massive asterisk on the impeachment itself, the way that the entire House process was run,” said Rep. Lee Zeldin (R-N.Y.). “And if Senator Schumer’s effort to rewrite history . . . will look back on what happened over on the House side — the fact is [the Senate] inherited a fatally flawed case, a fatally flawed process from the House.”

For Trump, the focus has been less on the history books and more on his reelection prospects, as he has used virtually every lever of persuasion at his disposal — from his Twitter account to a massive campaign account — to drive the message that the impeachment has been an unfair partisan witch hunt that misconstrued a “perfect phone call” with the Ukrainian president in July.

The argument was echoed in the Senate chamber during the trial by Trump’s defense team, which argued repeatedly that Trump did “absolutely nothing wrong,” and it is expected to persist well after the acquittal — with claims of vindication likely to stretch through the November elections and beyond.

While the outcome of the witness vote was in doubt until Alexander announced a no vote Thursday night, the likelihood of an acquittal was never seriously challenged. A conviction would require at least 20 Republicans to join with all 47 members of the Democratic caucus, and no more than a small handful of GOP lawmakers ever swayed publicly about the allegations that Trump used military aid and a White House meeting as leverage to force investigations of his domestic political rivals.

Trump’s maximalist defense, however, was undermined this week with such senators as Alexander and Rob Portman (R-Ohio) arguing that Trump’s behavior was in fact wrong, though not impeachable.

Republicans have anticipated, and Democrats have braced for, a Trump victory tour of sorts — one that, depending on how quickly the Senate can move to a verdict, could begin with Tuesday’s State of the Union address.

The “permanent asterisk” rhetoric this week has paved the road for the Democratic pushback for months, if not decades to come, by throwing doubt on the verdict.

“We know better,” Sen. Richard J. Durbin (D-Ill.) said of any claims of vindication. “He’s going to talk about the end of the ‘witch hunt’ and so forth, but I think the fact that the Republicans are so afraid of a trial and so afraid of the truth speaks for itself.”

Said Sen. Kamala D. Harris (D-Calif.), “You cannot have a true acquittal if you’ve not had a fair trial.”

“No witnesses means no exoneration,” Sen. Brian Schatz (D-Hawaii) tweeted Friday.

Democrats say their incessant public campaign for “witness and documents” — one that began with Pelosi’s surprise decision to hold out on naming managers and formally sending the articles to the Senate — will ultimately pay political dividends as Americans turn away from the impeachment saga and toward the presidential race.

“The way in which Republicans have conducted this will allow Democrats for the next 10 months to draw issue with Trump’s acquittal which we wouldn’t have been able to do if we had come to an agreement on rules and we had had witnesses and we had had deliberations,” said Sen. Chris Murphy (D-Conn.). “We now have legitimate reason to contest the fairness of the trial and the acquittal of the president, and I think that’s impactful.”

Paul Kane and Seung Min Kim contributed to this report.