The intense outreach began right before Trump released a read-out of his call with Ukrainian President Volodymyr, when Trump called into a White House meeting with senators and House Republicans to review the conversation before its public release. Then in late October, Trump began hosting lunches with roughly nine GOP senators at the White House.

In the lunches, Trump has told senators to review his phone call with Zelensky, cited moderate Democrats’ opposition to impeachment and complained about the House process. But he and GOP senators have also discussed strategic questions that could help shape the Senate trial.

At one lunch, Sen. Kevin Cramer (R-N.D.) asked Trump whether he preferred Senate Republicans to quickly clear Trump and dismiss any articles of impeachment or hold a longer trial that allows his lawyers to more fully defend him. The president’s response surprised Cramer: “You guys will have to figure it out.”

In Cramer’s view of the lunches, Republicans "weren’t there as part of a strategy session, we were there as probably more of a discovery session.”

One White House official said the gatherings have been helpful to get synced up with GOP senators but added “it’s too simplistic” to think everyone is automatically on the same page. "They have their agenda, and we also have ours," said the official.

The low-key approach from Trump reflects a lighter touch since Senate Majority Leader Mitch McConnell (R-Ky.) urged him to avoid attacking sitting GOP senators who criticize him.

Collins has rebuked the president for asking China to probe Biden and has been quicker to push back against Trump’s controversial conduct and rhetoric than most Republicans.

But Collins has also studiously avoided commenting on the impeachment proceedings because of her likely role as a juror in a Senate trial. A person familiar with the White House meeting set for Thursday confirmed her attendance.

In addition to Collins and Romney, GOP Sens. Chuck Grassley of Iowa, James Lankford of Oklahoma, Rand Paul of Kentucky, John Hoeven of North Dakota and Shelley Moore Capito of West Virginia have been invited to the lunch on Thursday. Senators are not given a list of fellow attendees beforehand, nor are they given an agenda before heading to the White House to dine with the president.