New Hampshire has been good to Bernie Sanders, delivering him a 22-point victory in 2016 that was one of his biggest blowouts that year. But as he launches his second campaign for the presidency, there are early signs that he doesn't have a lock on the nation's first primary.More than a half-dozen Democratic leaders, activists and lawmakers who endorsed the Vermont senator in 2016 said they were hesitant to do so again. Some said they were passing over the 77-year-old self-described democratic socialist in search of fresh energy while others said that, 11 months away from the primary, it's simply too early to make a choice. That caution underscores one of the central challenges facing Sanders. His insurgent 2016 campaign took off in part because he was the sole alternative to the more establishment-oriented Hillary Clinton. But in a 2020 field that already spans a dozen candidates and includes several progressives, women and people of color, Sanders isn't the only option for people yearning for political change. "He's right on many of the issues that I care about,'' said Jackie Cilley, a former state senator who endorsed Sanders in 2016. "But I'm just looking at some new candidates." With his name recognition and residency in neighboring Vermont, Sanders goes into New Hampshire with an early advantage. But his rivals aren't ceding the state to him. On a recent New Hampshire swing, California Sen. Kamala Harris insisted she would compete for the state and took a not-so-subtle dig at Sanders by noting she's not a democratic socialist. Sens. Elizabeth Warren, of neighboring Massachusetts, along with Cory Booker of New Jersey and Kirsten Gillibrand of New York, have also visited New Hampshire.Endorsements aren't the only sign of a candidate's strength. And Sanders and his team insist they won't take New Hampshire for granted. His first swing through early-voting states this week as a 2020 presidential candidate includes several stops in New Hampshire. The senator plans to spend "a lot of time" in the state, said Jeff Weaver, Sanders' 2016 campaign manager who is now working as a senior adviser for the new campaign. He acknowledged it would be difficult for Sanders to notch as big of a victory in New Hampshire as he did in 2016. "In a very big field, it will be impossible to get that kind of margin again," Weaver said. Several Democrats said the size of the field has made them think twice about backing Sanders too quickly. "It's massive," liberal activist Dudley Dudley said of the 2020 roster. "Our cup runneth over or something, I don't know. I'm struggling with it myself." Dudley said she's still fond of Sanders but has also been impressed by other senators who have visited New Hampshire, including Sherrod Brown of Ohio. "If I were to endorse [Sanders], it would be because I believe he is the most likely to be able to beat [President Donald] Trump,'' she said. "And it may come out that way. I don't know. But I want to weigh it. I want to look at all of the candidates." Steve Marchand, the former mayor of Portsmouth, endorsed Sanders in 2016 but described himself as ``wide open'' when it comes to 2020. "I'm not going to support anybody for a good long time,'' Marchand said. "I want to kick the tires on everybody." Another hurdle for Sanders is one of his own making. His leftward push against Clinton in 2016 proved so popular among Democrats that it's now become vogue for the younger generation of 2020 candidates. Looking at the crowded 2020 field, former state Sen. Burt Cohen said it seems like Sanders' 2016 agenda is "pretty much everybody's agenda," including "Medicare-for-all" and criticizing income inequality. After endorsing Sanders in 2016 and working as a delegate for him at the Democratic National Convention, Cohen hasn't "fully decided yet" whether he'll support Sanders, saying, "I may end up endorsing Bernie. I'm not sure." The approach is shared by fellow 2016 Sanders delegate Andru Volinsky, who now holds a seat on the state's executive council. "My initial inclination is towards Sen. Sanders," Volinsky said. "But the door is not completely closed to others." Despite the caution from some Democrats, others have already embraced his 2020 run. Sanders has kept the support and help of Kurt Ehrenberg, who was the New Hampshire state director for the unsuccessful effort to get Warren to run during the 2016 cycle. He then became the New Hampshire political director for Sanders during the presidential campaign. Rep. Mark King, a Nashua Democrat, endorsed Sanders in 2016 and said he plans to do so again, in part because Sanders has the same values and the same approach as he did before. "I didn't just blindly follow the senator again," said King, who was a 2016 delegate for Sanders.