WASHINGTON (WPRI) – U.S. Sen. Sheldon Whitehouse is warning fellow Democrats that presidential hopeful and fellow senator Bernie Sanders may not be ready for prime time if he manages to snatch the nomination from Hillary Clinton.

During an exclusive interview with WPRI.com, Whitehouse – a devoted Clinton supporter for many years – expressed personal affection for Sanders but said he feared the Vermont lawmaker would fare poorly against the GOP nominee in the November election.

“I think that in the very contentious, often bitter and mean atmosphere of presidential politics, when the Republican attack machine goes to work on somebody, they can do a lot of damage,” Whitehouse said. “And Bernie is completely untested against that machinery.”

“Maybe he shines through it all, maybe he comes through glorious and unhurt,” he said. “But maybe they tear him to pieces.”

If Sanders wins the nomination, “I think we’d have to fight really, really, really hard to win the election, even against terrible candidates for them like Donald Trump and Ted Cruz,” Whitehouse said. (As an aside, he speculated that GOP leaders could end up making House Speaker Paul Ryan the nominee at a brokered convention if Trump or Cruz is ahead in delegates.)

Whitehouse’s loyal support for Clinton is no surprise. The second-term Rhode Island Democrat has long lies to the Clintons, having been appointed U.S. Attorney for Rhode Island by then-President Bill Clinton in the 1990s. Whitehouse served as co-chair of Clinton’s 2008 campaign in Rhode Island, where she easily defeated Barack Obama in the primary eight years ago.

“I remain for Hillary because I think she’s far more electable,” Whitehouse said. “There is clearly a reason why 100% of the Republican attack machine effort has been devoted to Hillary. They know they’re going to face a much harder fight against Secretary Clinton than they are against Bernie Sanders.”

Still, Whitehouse took pains to praise Sanders, who was elected to the Senate the same year as Whitehouse and often sides with him on major progressive causes. “I adore Bernie, and I love seeing him succeed after all the effort that he’s put in over many, many years,” Whitehouse said.

Asked why he thinks Sanders is gaining on Clinton, Whitehouse said: “To a certain extent I think Bernie is getting the advantage of being in a bubble of no one saying an unkind word about him. Everybody doesn’t want to tangle with him – there’s no reason. I think everybody in the Senate loves him. And the Republican attack machine hasn’t even tried to throw a punch.”

“On the other side is Hillary, who they’ve been working at nonstop hammer and tongs for decades – about the Benghazi stuff, all that they’ve cooked and cooked and cooked,” he said.

“So what we’re seeing right now is the Election-Day Hillary Clinton competing with the announcement-day Bernie Sanders,” he continued. “And I think if Bernie’s the candidate, we will see that there’s a very different Bernie Sanders that is shown to the public by the Republican attack machine, and there’ll be a big difference between announcement-day Bernie Sanders and Election-Day Bernie Sanders, whereas Hillary Clinton’s been worked over so long by them that there’s not going to be a big change.”

Whitehouse’s senior colleague from Rhode Island, fellow Democrat Jack Reed, has also endorsed Clinton, as have the other two members of Rhode Island’s congressional delegation, Congressmen David Cicilline and Jim Langevin.

In his own interview with WPRI.com, Reed said he thinks Clinton will still win the nomination due in large part to her years of experience in government. But he gave credit to Sanders for winning so many supporters, and suggested geography is helping Sanders in New Hampshire.

“One has to recognize that Senator Sanders – who’s been a colleague for years, and someone who I personally like very much – has been in and out of New Hampshire all his political life, since he’s a senator from Vermont,” Reed said. “So I think a lot of it is proximity, and also I think he just has more connections, and I think that’s historic as much as anything else.”

The first votes in the 2016 presidential primary will be cast in one week, as Iowans gather to caucus on Feb. 1. The New Hampshire primary follows Feb. 9.

Rhode Island’s primary is not until April 26. Clinton and Sanders are among six candidates who pulled papers last week to compete in the Democratic primary and are currently gathering signatures to qualify, along with Martin O’Malley, “Rocky” De La Fuente, Lloyd Kelso and Mark Stewart.Ted Nesi (tnesi@wpri.com) covers politics and the economy for WPRI.com. He hosts Executive Suite and writes The Saturday Morning Post. Follow him on Twitter: @tednesi