Numerous hypothetical polls have favored Bernie Sanders over President Donald Trump for the 2020 presidential run.

However, Democrats themselves are well aware that Sanders’s efforts to outrun Trump have fallen through.

Ahead of the first debate, Sanders’s campaign intended to challenge Joe Biden to prove that he is more electable. But Sanders failed to aggressively confront Biden, and in the run-up to the second debate, his team took an alternative route to settle on a strategy to prioritize “Medicare for All.”

Sanders’s staffers admit they fear general-election backlash on their Medicare for All proposal, though they are willing to take the bet as they believe the same far-reaching health care proposal may eventually grab more supporters.

Sanders has attempted to persuade Democrats that he’s their best bet predominantly through data, though he has made efforts trying other approaches too. According to Politico, the Vermont senator took a four-day “electability tour” in April through Pennsylvania, Wisconsin, and Michigan—the Rust Belt states that played a substantial role in Trump’s 2016 victory—as well as other parts of the Midwest to prove that he can garner votes from working-class individuals.

In contrast to Elizabeth Warren, whose electability rose from 39 percent to 55 percent in the last three months, Sanders’s polling did not see too much change—52 percent of likely Democratic voters are placing the bet on Sanders, the same number as results from June.

Experts speculate that Sanders is facing electability challenges for numerous reasons. Democratic operatives have noted that Sanders is too liberal to beat Trump.

“Among the Democratic primary electorate, in some pockets, there’s fear of how he’s going to campaign on Medicare for All: ‘Are people going to get nervous and run away from it?’” Faiz Shakir, Sanders’s campaign manager said to Politico.

“I love Bernie,” New Hampshire delegate Gloria Hoag said at the state Democratic Party’s annual convention last weekend. “But I don’t know if he can beat Trump because he’s so far to the left. We need someone who’s a little more moderate.”

“His message tends to focus on what he wants to do and where he wants to take the country on issues. It’s not so much a comparison with Trump,” Iowa Democratic strategist Jeff Link said. “That’s probably why he hasn’t moved a lot. …Certainly Biden talks about Trump more.”

“This whole electability thing is overblown,” said Mark Longabaugh, Sanders’s top strategist for his 2016 presidential bid. “I remember the early feedback we got in 2015 in Iowa and New Hampshire: A lot of people said they loved Bernie’s message, absolutely loved it, but they just assumed Clinton was going to win. Over time, as the campaign developed and his standing progressed, they stopped saying that. Because they liked him.”

What Longabaugh means is that electability comes naturally when a candidate succeeds through selling his or her values and issues.