Jodi Stanfield enthusiastically supported Bernie Sanders in 2016. Now, she has found a new candidate who excites her: Sen. Elizabeth Warren.

“I trust her when she says she can fight, and also win,” Stanfield said Saturday at a Democratic steak fry where many of the candidates spoke. While Sanders and Warren have similar platforms, the Massachusetts Democrat would be more effective in accomplishing her goals, said the 51-year-old, who works at the YMCA.

Stanfield represents a growing problem for the Vermont independent in his second run for president: Warren has begun to eclipse Sanders’s once-dominant standing among the Democratic Party’s most liberal voters and surpass him in some polls in the first two states in the nominating process: Iowa and New Hampshire.

They both support what would be a massive economic restructuring with ideas such as Medicare-for-all, but Sanders, 78, has carved out his brand as a democratic socialist while Warren, 70, has described herself as a capitalist who has operated more as part of the Democratic mainstream. While Sanders drew notice in 2016 for his avid fans and big crowds, it is Warren this time who is gaining traction that way.

These challenges have been compounded by volatility inside Sanders’s operations in Iowa and New Hampshire. The campaign quietly fired its Iowa political director in the late summer and has yet to name a replacement — a key vacancy as the race enters a crucial phase, with less than five months to go before the February caucuses.

Sanders’s difficulties in Iowa have come into sharper focus over the weekend. The most respected pollster in the state released a survey late Saturday showing Warren surging to 22 percent, two points ahead of former vice president Joe Biden, with Sanders at 11 percent. That places him third in the state where he fought Hillary Clinton to a near draw in 2016, launching an electrifying national movement.

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