-Analysis-

WASHINGTON — Bernie Sanders just made it official, announcing that he'll be a candidate for president in 2020. His candidacy brings lots of questions along with it, but the one I'd like to focus on for the moment is this: How is he going to present himself in relation to the party he wants to lead? Because that could turn out to be the biggest challenge he faces in getting the Democratic nomination.

One thing's for sure: Bernie is Bernie, and he isn't going to change. He's delivering the same message and talking about the same issues as he has since he began his political career almost four decades ago. If you ask him, he'll tell you that the country has finally come around to his way of thinking, and he'd have a good case to make. Just three years ago he was considered a radical for advocating things like a $15 minimum wage and Medicare-for-all, but now those are mainstream positions and nearly consensus among Democrats.

But there's another thing Sanders believes that also hasn't changed, and that could be a problem. He has built his identity on being an outsider, someone trying to force change from outside the system. And "the system" includes the Democratic Party, which he has always seemed to consider only slightly less corrupt than the Republican Party. Even after running for the Democratic nomination, he retained his official status as "Independent," though he caucuses with Democrats in the Senate.

In 2016, his status as an independent was the perfect place from which to launch a campaign against Hillary Clinton, the ultimate party insider and cautious technocrat. His critique of the political and economic system, combined with his uncompromising beliefs on issues, made for a clear contrast and attracted legions of idealistic young people who not coincidentally didn't have any other real options.

Just three years ago he was considered a radical.

This campaign will be very different, with at least a dozen other strong Democrats running. And one question Sanders will face is whether Democratic primary voters share his contempt for their party.

Or to put it more politely, his belief that the Democratic Party has to change if it's to succeed. The trouble is that argument is tougher to make after the 2018 election than it was before. Consider, for instance, this June 2017 op-ed Sanders wrote in the New York Times, in which he surveyed the state of the party and said, "If these results are not a clear manifestation of a failed political strategy, I don't know what is. For the sake of our country and the world, the Democratic Party, in a very fundamental way, must change direction."

Did the party change between then and the midterms? To a significant extent it did. A huge number of new people got involved in their local party organizations and decided to run for office, bringing an unprecedented grass-roots energy to the party. And on issues the party continued its leftward evolution, which you can see both in the stances the candidates are taking and in the beliefs of rank-and-file Democrats.

Take a look, for instance, at this report just issued by Gallup on the state of the Democratic Party. It shows that compared to what they believed 10 or 15 years ago, Democrats are more likely to call themselves liberal, more likely to have higher education and more likely to be nonwhite, all of which is helping to push the party leftward. The candidates are responding in many ways, all of which gives Sanders the ability to say that the party has come to him, whether it's the wide acceptance of universal health coverage or the fact that his competitors are now echoing his critique of the influence of the wealthy and corporations. Most of them have pledged not to take PAC money in their campaigns.

All of which may be satisfying for Sanders, but it also presents a problem. It's hard to be a rebel when the power you're fighting against doesn't disagree with you on all that much. And it may be even harder to argue that the power structure in your party needs to be overthrown when most of the voters you're appealing to aren't all that dissatisfied with that power structure, if it's being represented by a large group of interesting candidates.

Are the voters after a set of leadership characteristics? Charisma?

That isn't to say Sanders won't retain his most passionate supporters from the 2016 campaign. But his candidacy does raise this question: When primary voters choose a candidate, exactly what are they after? Is it a distinctive policy program? That makes it difficult, because the programs the candidates are offering will be so similar. There may be some people on social media who loudly proclaim that any candidate who doesn't favor precisely their preferred health-care plan is a sellout, but those voters are a tiny portion of the primary electorate. Are the voters after a set of leadership characteristics? Charisma? A general outlook on politics and government that matches theirs?

If there's anyplace where Bernie still stands apart, it may be on that last factor, that no one else has quite his commitment to fundamental change (or at least he'd say so). He'd also argue that only with his uncompromising commitment can change actually be achieved. And true to his activist identity, he says that the only path to change is by creating pressure from below to force it on an unwilling system. Here's part of what he said in his announcement video:

"The only way we will win this election and create a government and an economy that works for all is with a grassroots movement the likes of which has never been seen in American history. They may have the money and the power; we have the people."

He doesn't have them yet, but we'll see if he can mobilize them. To win the nomination he's going to have to convince Democratic voters that their party is a big part of the problem. And that may not be an easy sell.