One surprise call came from Air Force One as President Donald Trump was leaving Iraq, startling Sen. James Inhofe, R, as he was chopping wood back home in rural Oklahoma with his grandson.
When Sen. John Barrasso, R-Wyo., recently stepped off a plane, a White House voice mail was waiting for him, saying Trump was "available for the rest of the evening" for another round of their regular phone conversations.
Another recent call from Trump - this time to Sen. Joe Manchin, D-W.Va., was so unexpected that he crashed a Skype session between Manchin and a group of West Virginia high school students.
The chatterbox in chief has eschewed the traditional way that presidents communicate with members of Congress, calling lawmakers at all hours of the day without warning and sometimes with no real agenda.
Congressional Republicans reciprocate in kind, increasingly dialing up the president directly to gauge his thinking after coming to terms with the fact that ultimately, no one speaks for Trump but Trump himself.
"I never called President Bush or President Obama," said Barrasso, who has served in the Senate since 2007. "I just feel comfort in calling President Trump. He calls me regularly to talk about issues. He's always helpful for both of us."
Longtime senators who have served through multiple administrations say they have never seen a president so easily accessible to lawmakers. The calls are part of what occupies the wide swaths of "executive time" on Trump's schedule - an unstructured stretch of the day he uses to call allies and hold meetings that are otherwise not publicly announced.
Frequent phone partners
Senate Majority Leader Mitch McConnell - whom Trump has called while the Kentucky Republican was attending a Nationals baseball game - is among the most frequent of the president's phone partners.
But Trump also speaks often with Republican Sens. David Perdue of Georgia, Rand Paul of Kentucky, Lindsey Graham of South Carolina, Tom of Arkansas, Cory Gardner of Colorado, and Joni Ernst of Iowa, according to people familiar with the conversations.
Rep. Mark Meadows, R-N.C., chairman of the House Republicans' conservative faction and was once considered for White House chief of staff, also chats several times per week with Trump, mostly in impromptu calls.
"I've never seen anything like it," said one GOP senator who occasionally calls Trump, chuckling.
"It's a different world," said South Dakota Sen. John Thune, the No. 2 Senate Republican who is not one of Trump's regular phone partners but encourages senators to talk to the president directly.
Congressional Republicans patch through to Trump multiple ways.
One common route is through Madeleine Westerhout, the White House's director of Oval Office operations and a close aide to Trump who once served as the "greeter girl" for visitors at Trump Tower during the presidential transition.
Senators call her directly, and although Trump has given some Republican lawmakers his phone number, he tells most of them "just to call Madeleine."
For instance, Manchin has told others that he can reach the president directly by calling Westerhout, and that he is uninterested in talking to other White House staff members.
Other lawmakers go through the White House switchboard. For instance, Meadows primarily calls Trump that way for the sake of process, although he has used Trump's direct line before. And still others choose to dial Trump directly.
Although Republican senators who call the president say they usually do so with a specific agenda, his calls to them sometimes seem to have little point other than just to chat.
Talking TV and golf
Trump regularly calls senators if he sees news about their states. Other times, he talks about what he just saw on television or asks about golf.
Barrasso said their calls, usually about 10 minutes or so, span several topics and sometimes are prompted by a Barrasso appearance on cable television or a Sunday political talk show.
The president's penchant for trying to contact senators after watching them on television has forced his aides to scramble at times - White House officials who are unsuccessful reaching senators directly will often then track down their aides to say the president wants to talk.
When he calls, Trump bats around ideas with senators, asking for their thoughts about a policy move or a particular nomination. The day after his State of the Union address, Trump dialed at least one senator to get feedback.
And people around the senators when Trump calls often get the presidential touch.
When Trump called Inhofe from Air Force One as he returned from Al Asad Air Base in Iraq, the Senate Armed Services Committee chairman was with his grandson Jonah in Oklahoma, splitting logs. After Trump and Inhofe talked business, Jonah, 20, had a turn on the phone with the president, who effusively praised his grandparents.
Republican senators say they also have called Trump just to offer positive reinforcement and praise. Inhofe recalled going on a tour of rural towns throughout his state recently and receiving from voters about how much they adored the president.
"So I said, 'Mr. President, if . . . there are days when you're depressed because you think everybody hates you, I had this experience today,' " Inhofe said, recalling a conversation he had with Trump about a month ago. "Not one person was out there who didn't say, I love you."
One freshman senator who speaks with Trump regularly is Rick Scott, R-Fla., who has known Trump since before his political ascent and talks with him regularly on state-specific issues such as Everglades funding, hurricane aid and Venezuela policy. The two also talk about their shared background as executives, with Scott often sympathising with Trump as he's stymied by a legislature.
"I try to tell him . . . how I look at it and give him some ideas about how I look at things," Scott said. But "always understanding that he's the president and he gets to make his decisions."
Lawmakers rarely have to wait for Trump to return their calls - if they have to wait at all.
"The vast majority, he just picks up," said another GOP senator, who regularly calls Trump and spoke on the condition of anonymity to discuss private conversations. "If he doesn't . . . he'll return them within an hour."
Trump's phone habit is a clear departure from that of President Barack Obama, his immediate predecessor, who preferred formally arranged calls with a clear agenda rather than the freewheeling conversations favored by the current occupant of the White House.
Under Obama, calls with lawmakers were usually planned in advance through a brief discussion with the chief of staff or the legislative affairs office, said a senior Obama White House official who spoke on the condition of anonymity to discuss how calls with lawmakers are handled. After the call, Obama would read out the conversation to aides - although White House staff members would often accompany the calls - and the information was shared among the relevant officials.
"I cannot recall Obama phone-bombing people for anything substantive," the senior official said.
While Obama and President George W. Bush had a more formal approach to discussions with lawmakers, President Bill Clinton was known for calling members of Congress, sometimes late at night, to discuss policy debates.
The conversations between GOP lawmakers and Trump also reflect doubt among Senate Republicans about whether they can get an accurate read on Trump's thinking from anyone but Trump himself - a dynamic that became painfully acute as Washington barreled into a shutdown in December.
Back then, Senate Republicans came away from a private meeting with Vice President Mike Pence assured that Trump would sign a short-term spending bill without a significant boost in border wall money, only to have Trump completely reverse course less than 24 hours later.
And Pence and Acting White House Chief of Staff Mick Mulvaney also privately floated a smaller figure for wall funding to Senate Minority Leader Charles Schumer, D-N.Y. - only to have Trump reject that figure publicly days later.
GOP senators say that although Trump's main legislative liaison, Shahira Knight, is responsive, she is generally unable to speak for the president. During one recent meeting on Capitol Hill, Knight called Trump twice to ask whether certain proposals being floated would be acceptable, according to a person at the meeting. She was told no both times.
Mulvaney, despite his familiarity with Capitol Hill, can't speak for Trump either, aides said.
"That's the reason I call him," said one of the GOP senators who spoke on the condition of anonymity. "Because I can't be sure where everybody is."