CNN  — 

The universe of Republican senators who may be willing to cross the aisle and vote with Democrats to allow witnesses in the impeachment trial of President Donald Trump appears to be shrinking.

Three days of presentations by the House managers, and most Republicans say they are unmoved by the testimony, dismissing the arguments as repetitive and even boring, signaling that they may be ready to move on soon after the President’s defense team lays out its case. While a small group of moderate senators might be in play, even members up for reelection in 2020 in swing states Colorado, Iowa and North Carolina, have done little to signal they are wavering in their loyalty to Trump.

“Everyone handles foreign policy differently,” Republican Sen. Joni Ernst of Iowa said Friday. “I think there is a lot that goes on in administrations that we are not aware of, but is it an impeachable, unlawful offense? That has not been clearly demonstrated.”

After wall-to-wall coverage of a House impeachment inquiry in the House, weeks of public hearings with career diplomats accusing the President of a quid pro quo and damning transcripts putting the President’s personal lawyer at the center of the scandal, Senate Republicans are growing confident that this is now the defense team’s trial to lose.

“The House manager’s presentation has not been particularly effective. I try to be careful not to speak for other senators so I will just say in general, the chatter I hear is ‘is that really the best they can do?’” said Sen. Josh Hawley, a Republican from Missouri.

Republicans are heading into the next phase of the trial hoping – albeit aware of Trump’s tendency to be a wild card – that the President’s defense team follows the mantra of do no harm. Yes, they say, Trump’s team will need to poke holes in the Democrats’ case. Yes, they the team will need to explain why nearly $400 million in military aid was withheld. But, what Republicans hope the team avoids is a drawn-out attack on the Bidens or any tangents that alienate moderate Republican senators whose votes on witnesses are on the line.

“I would keep it high minded on the law. I would be aggressive about that the (Democrats’) facts don’t support (their case), they have cherry-picked witnesses. If I could find spots where the witnesses said one thing, but they meant another, I would do that. I wouldn’t spend 24 hours. I wouldn’t get personal with the Bidens,” said Trump ally Sen. Lindsey Graham, a Republican from South Carolina. “The problem I’ve got is I know Joe and he’s not a corrupt man. He is a good man, but I don’t know what Hunter Biden did in the Ukraine.”

Jay Sekulow, a leader on the President’s defense team, told reporters Friday night that “sometimes less is more.”

“I will say this. If our team decides we need to take the full time, we’ll take it. If we don’t, we don’t.”

Republican Sen. John Barrasso of Wyoming offered his blunt advice: “They need to not take us until two in the morning.”

All eyes have been on moderate Republicans – four in particular – and whether Democrats’ arguments would be enough to sway them to vote for witnesses including former national security adviser John Bolton or acting White House chief of staff Mick Mulvaney, but in recent days even those members’ are signaling they may not ultimately vote for witnesses.

“I think the House managers have had a more than fair opportunity to present their case. That is what they have asked for and that is what we have given them,” said Tennessee Republican Sen. Lamar Alexander. “I think the House managers have done a good job of making their arguments, but that doesn’t mean I will agree with them.”

Behind the scenes, Republican leadership has pressed the case that a vote for witnesses could turn a 10-day impeachment trial into a unending political free-for-all in which the ultimate outcome – the President’s acquittal – is still almost all but guaranteed. Asking for witnesses, leaders have said, would almost certainly force the case into court over questions of executive privilege and delay the Senate’s ability to move on.

“The House made a decision that they didn’t want to slow things down by having to go through the courts,” moderate Republican Sen. Lisa Murkowski of Alaska told CNN. “And yet now they’re basically saying you guys gotta go through the courts. We didn’t, but we need you to.”

While the most-watched senators – including Murkowski, Alexander, Mitt Romney of Utah and Susan Collins of Maine – have all said they will wait to make up their minds on witnesses until after they hear the presentations from both sides, fellow Republicans argue the President’s lawyers job in the days ahead should be to simply not do anything to alienate the senators on the line.

“They need to put on a defense. Our members are looking for a counter narrative,” said Sen. John Thune, the majority whip. “I think it is important they get out and take issues head on.”

CNN’s Alex Rogers contributed to this report.