Sen. Bernie Sanders may find himself mobbed as he moves about the nation stoking the flames of all those feeling the Bern. But back here in the Senate, his embers are cold.

About 40 Senate Democrats have lined up behind Hillary Clinton’s presidential campaign. Not one has come forward for Sanders.

Sanders’ loner status was brought into sharp relief last week when Sen. Harry Reid of Nevada, the Democratic leader, declared Clinton his pick. “I think the middle class would be better served by Hillary,” he said.

Senate Democrats insist Sanders is not their version of Sen. Ted Cruz of Texas, who has failed to get a single Republican Senate endorsement in large part because he is loathed.

'There’s a lot of history there'

Everyone likes Bernie. Even, they say, if he is like your father’s childhood friend who sits at the dinner table after everyone has had a second cup of coffee to continue his rant about the earned-income tax credit.

“It’s totally positive. It is not negative toward anyone else,” said Sen. Barbara Boxer, D-Calif., an early endorser of Clinton. “That’s the difference between our side and theirs. Also, don’t forget many of us did serve with Hillary in the Senate, so there’s a lot of history there.”

(Boxer did not point out that she has served longer in the Senate with Sanders — nine years and counting — than she did with Clinton.)

More qualified and electable

Democrats say they find Clinton — the former first lady, senator from New York and secretary of state, who has raised millions of dollars for them over the years — simply more qualified and more electable. Their position is underscored by Clinton’s 47-percentage-point trouncing of the self-described democratic socialist in the South Carolina primary on Saturday. Clinton prevailed in three of the first four primary states.

“Before I endorsed Hillary I spoke to Senator Sanders out of respect,” said Sen. Chris Coons, D-Del. “I think he is passionate about income inequality. I just think that Secretary Clinton has a unique set of experiences and insights to be the next president.”

A socialist at the top of the ticket

Also, Democrats who have concerned themselves with the party’s taking back the Senate, like Sen. Claire McCaskill of Missouri, are not so excited about having a socialist at the top of the ticket.

For Sanders, who has largely kept to himself in the Senate, this is probably OK. Endorsements from the establishment are no help at all these days. Just ask Sen. Marco Rubio, who was endorsed by the popular Republican governor of South Carolina, Nikki R. Haley, but was trounced in the state’s primary by Donald Trump.

'Endorsements don’t mean much'

On top of that, in running away from the establishment, Sanders is hardly seeking approval from his peers.

“For Sanders, legislative endorsements don’t mean much,” said Julian E. Zelizer, a professor of history at Princeton University. “His argument is that the system is broken, so support from that very system is not expected and in certain respects would undercut his basic message. So on that front he is in a good position, where the absence of support can be a source of strength, in contrast to Clinton, who wants to let voters know she is in fact the candidate who would be able to move things on the Hill.”

A Sanders campaign spokesman did not return emails seeking comment.

Gun control central to Clinton

In at least some cases, senators are able to cite specific issues that have drawn them to Clinton.  Sen. Christopher S. Murphy, D-Conn., who has devoted his career to gun control legislation since the 2012 massacre at Sandy Hook Elementary School, specifically cited Clinton’s record in an op-ed article in The Hartford Courant.

“We need leaders who don’t simply check the right boxes on the issues we care about, but who are champions day in and day out in the fight against gun violence,” he wrote. “By that measure, there is only one presidential candidate who qualifies.”

Sanders enraged some gun control advocates over the years with his support of gun rights legislation. Former Rep. Gabrielle Giffords, a Democrat who was shot in the head during an event in Arizona in 2011, appears in an ad in support of Clinton on the issue.

'Who can defeat the Republicans?'

But most senators have a broad view that Clinton would be the stronger contender against any Republican who won the party’s nomination, even though early polling shows various results.

“If you care about who can defeat the Republicans, who can lead the top of the ticket so we can get a majority back and who, once there, has the most capacity to get something done, it’s her,” said Guy Cecil, the head of Priorities USA Action, a “super PAC” supporting Clinton. “Also, Hillary has been very focused on building a Democratic infrastructure, not just for her election but for state legislatures on up, and that is something that is encouraging to them.”

Sanders allies go to Clinton or go silent

By contrast, Sanders, who has been elected as a Vermont independent but caucuses with Democrats, has never been a party loyalist. He is more concerned with finding partners on issues he cares about — income inequality, Social Security expansion, affordable college — than with building political coalitions.

Still, even Democrats with whom he is best aligned, like Sen. Sherrod Brown of Ohio, have given their support to Clinton. Or they have remained silent, like Sen. Elizabeth Warren of Massachusetts.

'I’d choose Hillary'

This is a shift for Clinton, who in 2008 split her colleagues with Barack Obama, a senator whose candidacy caught on with other Democrats far later in the game.

“We all respect Senator Sanders a great deal,” said Sen. Benjamin L. Cardin, D-Md. “My support for Hillary was there long before Bernie Sanders’ campaign took roots. But if I had to make that choice again, I’d choose Hillary. She is so uniquely qualified to be president.”

Like his colleagues, Cardin said he bore Sanders no grudge, especially since Sanders does not appear to be much of an impediment to Clinton’s expected romp through Super Tuesday this week. “His campaign has been electrifying to the process,” he said.