DES MOINES, Iowa — President Donald Trump's defense lawyers rested with more of a whimper than a bang Tuesday — resigned, perhaps, to the possibility that their boss's time in the crucible of a Senate impeachment trial will not come to an immediate end.

Trump's lawyers even appeared to undermine their own assertions that former national security adviser John Bolton, whose forthcoming book reportedly corroborates the allegation that the president tied U.S. aid for Ukraine to political investigations, should not testify.

Facing stiff headwinds in the form of growing Senate interest in hearing Bolton's story and national polling showing strong public support for witness testimony, the president's defense team quietly appealed for a summary acquittal.

"It will show that you put the Constitution above partisanship," White House counsel Pat Cipollone told senators in closing a nearly three-hour presentation by the defense. "It will show that we can come together on both sides of the aisle and end the era of impeachment for good. ... You know it should end."

Trump's team wants to shut it all down as soon as senators have had their 16-hour question-and-answer session, which begins Wednesday. No witnesses. No new documents handed over to lawmakers.

Ron Bonjean, a former Senate Republican leadership aide, said there's no value to the GOP in extending the discussion."The best path forward is to end the trial as quickly as possible because the president is going to be acquitted," he said. "Bringing witnesses only prolongs the inevitable, and Senate Republicans will continue to play on Democratic turf."

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But most signs in the Senate, where Trump remains all but certain to win acquittal eventually, point to a handful of Republicans wanting to receive more evidence before they render a judgment.

The Bolton bombshells — his book also reportedly records concerns that the president did "personal favors" for the leaders of China and Turkey — clearly have forced Senate Republicans to reconsider whether they are willing to take on the political risk of clearing him when potential witnesses could reveal more damaging evidence after his trial. Moreover, Senate Republicans have accused House Democrats of jamming through a partisan impeachment in the first place.

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That raises the question of whether shutting down witness testimony just as new, relevant information surfaces outside the trial would leave GOP senators in tough re-election races vulnerable to claims that they put partisan interests ahead of a fair trial.

"Some of the people who have expressed their opinions, they are grappling with that," Sen. Mike Braun, R-Ind., said of his colleagues in an interview on NBC on Tuesday.

The Trump defense team's effort to dismiss the need for Bolton's testimony may have had the reverse of the intended effect. Jay Sekulow argued to senators that Bolton's allegations have no bearing on whether the president should be removed from office, using fellow Trump defense counsel Alan Dershowitz's contention that "abuse of power" is a phony construct.

"It follows from this that if a president, any president, were to have done what the [New York] Times reported about the content of John Bolton's manuscript, that would not constitute an impeachable offense," Sekulow said. He went on to cite proclamations by the president, an aide to Vice President Mike Pence and the Justice Department on behalf of Attorney General William Barr that the excerpts reported on by the Times are inaccurate with respect to the principals in question.

But if all of those figures are telling the truth, they should want Bolton to testify under penalty of perjury. And if the president has nothing to lose — if abuse of power isn't a real reason for removing a president from power and Trump didn't abuse his power, as his lawyers have argued — there's no harm in having Bolton testify.

The benefit of leaving no stone unturned before acquitting Trump obviously has occurred to Senate Republicans who will face voters in November.

And in detailing the reported allegations, the lawyers served to highlight what Bolton has to offer.

"Are you going to allow proceedings on impeachment to go from a New York Times report about someone that says what they hear is in a manuscript?" Sekulow said. "Is that where we are? I don't think so. I hope not."

Aside from him, Trump's lawyers spent their final hours building partisan sympathy for a president under investigation throughout his term in office, even as they decried polarization in the country and called for unity. They repeatedly said Trump applied no pressure to Ukrainian President Volodymyr Zelenskiy to open investigations into former Vice President Joe Biden and "Crowdstrike" — the shorthand for a Russia-originated disinformation campaign designed to obscure Moscow's role in aiding Trump's 2016 election.

Deputy White House counsel Patrick Philbin acknowledged in one moment that Congress sets constraints on the president's policy-making by passing laws — then said it's impossible for the president to act in contravention of U.S. foreign policy interests, as he's alleged to have done in withholding the assistance for Ukraine, because he's the one who determines them. Some of the senators who voted to give Ukraine $391 million may have a different view.

In the end, after six days of arguments from House managers and White House defense lawyers, the basic facts were undisputed.

Trump dispatched administration officials to work with his personal lawyer Rudy Giuliani on Ukraine matters while Giuliani was focused on pursuing political investigations.

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Trump discussed four items on a July 25 phone call with Zelenskiy: how much aid the U.S. provides to Ukraine relative to other countries, the Biden investigation, the Crowdstrike investigation and a prized White House meeting that Zelenskiy had been seeking for months. After calling attention to the money, Trump told Zelenskiy, "I want you to do us a favor, though," and proceeded to detail the probes he wanted.

And at the time of the phone call, Trump already had frozen $391 million in congressionally appropriated assistance. The freeze would last two months, as Ukrainian officials scrambled to figure out how to get it flowing again, and, according to the Government Accountability Office, administration officials violated federal budget law in carrying it out.

Witnesses who testified before the House said Trump was personally obsessed with the investigations, and that the aid was tied to Zelenskiy announcing them.

On Tuesday, the president's defense team didn't refute those facts — and they may have made a more compelling case for calling Bolton to testify than for closing the trial without him.