WASHINGTON — Slow your roll, Joe.

That’s the message several of former Vice President Joe Biden’s rivals for the Democratic presidential nomination are sending with their recent campaign moves.

“This field is going to be winnowed out pretty quickly,” Biden, the current front-runner, told reporters in Los Angeles this week. “...It’s going to work its way through relatively quickly for all of us.”

But the rest of the field is offering fresh evidence that it is preparing for a long nomination fight.

After a period of big broadcast-news celibacy, former Texas congressman Beto O'Rourke is scheduled to appear on ABC's "The View" Tuesday, shortly after his campaign's Thursday announcement that it had added to its arsenal Jeff Berman, the delegate and party rules guru who helped engineer Barack Obama's 2008 primary victory.

The TV audience will get bigger play among Democratic voters, but for political insiders, party donors and the media, the Berman hire was an unmistakable sign that O'Rourke is loading up to wage a long war for the nomination. Why else would would the campaign need a delegate expert?

O'Rourke's campaign manager, Jennifer O'Malley Dillon, told NBC News that his team is ready for either a protracted primary or a race that he can lock down quickly.

"I believe we will be prepared for both scenarios," she said in a text message.

Telegraphing the possibility of a long-slog delegate fight — and recognizing the reality of Biden's early strength — is also a useful frame for Sen. Kamala Harris, D-Calif., currently emphasizing the value of voters of color in key swing states that President Donald Trump won in 2016.

"There has been a conversation by pundits about ‘electability’ and ‘who can speak to the Midwest,'" Harris said at an NAACP dinner in Detroit Sunday. "It leaves out people in this room, who helped build cities like Detroit."

Minority voters make up a tiny share of the electorate in Iowa and New Hampshire, but are critical for racking up delegates later in the primary season. Harris has been campaigning recently in states like Georgia, Michigan and Ohio, which hold their primaries deeper into the calendar, contain delegate-rich big cities with large African-American populations and could be competitive in the general election.

Harris' case against the "electability" argument for Biden revolves around the idea that the Democratic nominee will need a coalition that includes an energized contingent of voters of color. Right now, Biden is not only the far-and-away leader in the Democratic race, with a 41.4 percent mark in the Real Clear Politics average of polls, but he is the favorite among black and Hispanic voters.

And since Biden’s entry, in concert with his own rise into the midst of the lead pack trailing the former vice president, South Bend, Indiana Mayor Pete Buttigieg has begun to show a new interest in engaging with African-American leaders and voters. He met with the Rev. Al Sharpton, a former presidential candidate and MSNBC host, in New York at the end of last month and has made forays into predominantly black communities in South Carolina in recent weeks.

Ultimately, what all of these moves amount to are both a concession and a declaration by the rest of the field: Biden's powerful launch last month has knocked everyone else a bit off stride — but they want voters, donors and pundits to know they're limbered up for a marathon.

While O'Rourke, Harris, Buttigieg and most of the rest of the riders on the 2020 Democratic nomination party bus have been reluctant to directly attack Biden, who remains highly popular with Democratic voters, Sens. Bernie Sanders, I-Vt., and Elizabeth Warren, D-Mass., have been far sharper in their critiques.

Warren personalized a policy contrast in Cedar Rapids, Iowa, last month, portraying herself as a lone populist champion against Joe and The Establishment.

"At a time when the biggest financial institutions in this country were trying to put the squeeze on millions of hardworking families who were in bankruptcy because of medical problems, job losses, divorce or death in the family, there was nobody standing up for them," she said. "I got in that fight because they just didn’t have anyone. And Joe Biden was on the side of the credit card companies."

Sanders has been unflinching in his criticism of Biden's votes for trade deals and the Iraq War, setting himself apart from the field in that way.

"Joe is a good friend of mine and I'm not here to attack Joe," Sanders said recently before laying out differences he thinks should matter to voters. "Joe voted for the war in Iraq, I led the effort against it. Joe voted for NAFTA and permanent trade agreement, trade relations with China, I led the effort against that."

Whether it's a long fight or a short one, Biden appears to have determined that his best path is to keep focused on Trump and ignore any slights from his primary rivals.

But for as long as he's in the pole position, his competitors will have to find ways to reassure their supporters — particularly the donors who fund their campaigns — that they won't be scared off easily and that they can withstand any early show of force from Biden.

That can be hard to do in the weeks when the only measure is polling and there aren't events like debates or primary elections that can shake up the dynamics of the race. The first debate of the primary season, which will air on NBC, MSNBC and Telemundo, is in Miami on June 26 and June 27, with 10 candidates participating on each night.

But now Berman, known as an expert on delegate rules and a force in the party's rewrite of its nominating rules for the 2020 election, will serve a breathing advertisement for O'Rourke's confidence in the sustainability of his operation.

"This is a big get for @BetoORourke," David Axelrod, a former top Obama adviser, wrote in a tweet just after the news was announced. "Jeff Berman is a brilliant student and navigator of the Dem delegate process. It really does matter."

As Berman himself put it to NBC in January, a multi-candidate race could turn into a lengthy, brutal fight for delegates — precisely the scenario Biden, who said last week that “the process is already too long,” would like to avoid.

"It could be like 'Lord of the Flies,'" said Berman.