And the White House appears to have noticed.
Coons was the only Democrat from a solidly blue state invited to a meeting between President Donald Trump and eight other senators last week. Republicans have 52 seats in the Senate and would need eight more votes to avoid a filibuster on key issues such as the confirmation of Supreme Court nominee Neil Gorsuch — making every Democratic vote potentially significant.
Coons, who sits on the Senate Judiciary Committee, has refused to go as far as some of his Democratic colleagues and call for a filibuster of Trump's Supreme Court nominee, saying he wants to move forward "one step at a time" and first hold a hearing and committee vote before deciding any further action.
That doesn't mean he's completely ruled out a filibuster, however. Coons meets with Gorsuch on Tuesday, and he intends to press him on a number of issues, including how Gorsuch would handle further attacks on the judiciary by the President. He's hoping Gorsuch will go beyond comments he made to Sen. Richard Blumenthal, a Connecticut Democrat, who said the nominee called Trump's criticism "disheartening" and "demoralizing."
"We are going to have a constitutional crisis if this President continues in the direction he's headed," Coons told CNN in an interview. "Three weeks as President and this is one of those red lines."
Coons said "judicial independence" is fundamental for constitutional order. "And if Judge Gorsuch doesn't get that, he doesn't belong on the court."
Still, while some progressives are calling for Democrats to do whatever they can to stall or block Trump's nominees —especially after Republicans blocked President Barack Obama's Supreme Court nomination last year — Coons has been hesitant to commit to similar stonewalling.
He said it was "outrageous" that Republicans refused to give Merrick Garland a hearing last year and that it's "only human to want some revenge," but Democrats need to challenge themselves not "to act in a petty way."
"If all we do is continue to exact a pound of flesh from each other, we will eventually strip our republic bare to the bone," Coons told reporters recently.
CNN has reached out to the White House for comment on their relationship with Coons but hasn't yet gotten a response.
Coons is keenly aware of the reality that Democrats aren't in control.
"We don't run the Senate. They can have hearings for Judge Gorusch without us--whether we like it or not," he told CNN. "The reality is he's going to get a hearing on the judiciary committee. The challenge is will we fully participate? The more narrow point is: Am I keeping an open mind?"
Coons' name has popped up a few times in recent months in association with Trump.
Along with the White House meeting last week, Coons appeared with Trump at the National Prayer Breakfast earlier this month, and made a visit to Trump Tower back in December.
The incident raised eyebrows since Coons hails from a blue state where Democratic presidential nominee Hillary Clinton clobbered Trump, 53%-42%. He's also not up for re-election until 2020, so he's not under as much pressure as some other Democrats who are defending their seats next year, especially those from red states that Trump won.
But his recent sightings with Trump don't necessarily suggest the two are striking up a bromance.
Coons was the co-chair of the National Prayer Breakfast, so naturally the two would be seen together at the event. As for his visit to Trump Tower? That was made to formally invite Trump to the breakfast.
The two also traveled to Dover Air Force Base together for the return of the remains of the US service member killed in the raid in Yemen, a relatively common practice for Delaware dignitaries.
In fact, there's plenty of evidence of Coons being critical of Trump, especially during the presidential campaign but also since Trump's inauguration. Coons once called Trump "a thin-skinned reality TV star" and "a Cheeto-faced short-fingered vulgarian," according to reports. (He later expressed regret over the comment.)
Coons has so far opposed six of Trump's Cabinet nominees -- Steve Mnuchin, Betsy DeVos, Jeff Sessions, Tom Price, Nikki Haley and Mike Pompeo -- and approved three of them--John Kelly, Elaine Chao and James Mattis.
He did not vote on Rex Tillerson for secretary of state because he was on the trip to Dover with Trump during the full Senate vote. And while he told MSNBC that he was considering voting for Tillerson out of concern for whom Trump might pick should Tillerson fail confirmation, he ultimately voted against the former ExxonMobil CEO in the Senate Foreign Relations Committee vote.
Nonetheless, Coons has been adamant that he's willing to work with the other side.
"I think the only way we have any hope of getting back to a functioning Senate is if we follow the rules and traditions of the Senate," he said.
'The Delaware way'
Coons' outlook may be influenced by home state values. Shortly after every Election Day, Delaware has a state holiday called "Return Day," where people gather in Sussex County to announce and celebrate election results. The tradition dates back as far as 1792.
Candidates, both winners and losers, ride together in a parade of horse-drawn carriages and antique cars, then opponents pair up to bury a hatchet in a box of sand. Coons did so in 2010 with his Republican Senate rival, tea party favorite Christine O'Donnell, creating a rather surprising photo opp at the end of a bruising political year.
"I've grown up going to that for decades and it's an important part of our state's culture," Coons told CNN. "We talk about something called the Delaware way, which is how we manage to work together across the aisle."
That same spirit of bipartisanship was also on display when Delaware's new Democratic Gov. John Carney brought his gubernatorial rival as his guest to Trump's inauguration.
And Coons invited Trump's Delaware campaign chair, Rob Arlett, to the National Prayer Breakfast as his guest. The two men, despite their wildly different political views, say they have a mutual respect for each other, in part because their sons are both high school wrestlers in the same weight class for opposing schools.
Speaking to CNN, Arlett recalled what he considered a remarkable exchange with the senator at an event on Return Day, when Coons came up to Arlett and shook his hand to congratulate him on Trump's win. Coons added that he went onto Trump's website and found three items among Trump's goals for the first 100 days that the senator felt he could start working on with the administration. They involved veterans, infrastructure and manufacturing.
"That was the first conversation that he and I had after the election," Arlett said. "A handshake and an agreement that we have to work together."
Growing up Republican
Coons grew up as a Republican in a conservative family and volunteered for Ronald Reagan's presidential campaign in 1980. He became a Democrat in college, but he said his background helped him better understand the other side.
"When I walk into a room with a Republican senator, I don't walk in assuming that they are mean spirited or wrong headed. I think 'Oh, you know, this person has the view of this uncle or that cousin,'" he said. "I think that helps."
Sen. Johnny Isakson, a Republican from Georgia, has worked with Coons on a number of committees as well as legislation and praised his Democratic colleague to CNN Monday. The two formed a friendship not only through legislating but also at the weekly prayer breakfast in the Capitol, according to Isakson, who added that they've "become best of friends."
"He legitimately tries to find common ground," he said. "The last question he asks is what party are you from, not the first question."
Sen. Bob Corker, a Republican who chairs the Senate Foreign Relations committee on which Coons serves, has also worked with the senator on legislation. He painted Coons as "open minded" and "incredibly diligent," though he doesn't agree with him on everything.
While Coons described the President as "alarmingly ungrounded in the traditions of our Constitutional system," he said he's determined to work with his colleagues to restore what he sees as a sense of order, even if it can feel instinctual to do the opposite during such highly-charged, emotional times.
"I think the role of the Senate is more important than ever," he said.