Democratic presidential candidate Bernie Sanders speaks to a crowd of 7,000 in Birmingham, Ala., on Monday. (Brynn Anderson/AP)

Democratic presidential hopeful Bernie Sanders is preparing for a protracted battle with Hillary Clinton by hiring staffs and laying groundwork in more than a dozen contests that follow Iowa and New Hampshire, the first two nominating states.

Sanders has deployed about 50 paid campaign aides apiece to Nevada and South Carolina, the next two states on the calendar, according to advisers. Paid staffs are on the ground in all of the 11 “Super Tuesday” states that have contests on March 1, a presence that appears to at least match that of the Clinton camp.

The Vermont senator is also airing TV ads and Spanish-language radio spots in Nevada. He is about to go on TV in South Carolina. And his team is mapping out plans to spend a fresh wave of small-dollar donations expected to arrive if he upsets Clinton in Iowa or New Hampshire, as recent polls indicate is possible. That money, aides say, would allow Sanders to compete with the former secretary of state and Democratic front-runner in the crush of contests that quickly follow on the calendar, as the playing field rapidly broadens and the election becomes more dependent on expensive television ads.

The preparations are part of an effort to buck what has emerged as the latest conventional wisdom surrounding the Democratic contest: that even if Clinton loses the first two contests, her superior campaign infrastructure and other advantages — including the demographics of the electorate — will allow her to overpower Sanders in subsequent states.

“There will absolutely be a very active contest after the first two states,” said Sanders’s campaign manager, Jeff Weaver, who disputed the oft-repeated notion that Clinton has a “firewall” in states that follow Iowa and New Hampshire. “A lot of time and effort have gone into developing our plans for the states beyond the first four.”

Speaking at a rally in Indianola, Iowa, Democratic presidential candidate Hillary Clinton said her supporters "can't wait" to see changes to health care. She contrasted her intentions with rival candidate Bernie Sanders's. (Reuters)

Clinton’s advisers say they also have paid staffs in all March 1 states, but they declined to share numbers. Aides also noted that Clinton has made at least one stop in each of the Super Tuesday states, with the exception of Vermont, Sanders’s home.

“Knowing this race would always tighten, our campaign has been building a strong grass-roots organization since day one to earn the nomination in the early primary states and throughout the primary and caucus calendar,” Clinton spokesman Jesse Ferguson said.

Despite the fresh preparations, Sanders, who represents a state that is 95 percent white, continues to trail Clinton among Latino and African American voters, who make up large shares of the Democratic electorate in Nevada, South Carolina and many of the March 1 states.

Clinton has led in the few polls that have come out of Nevada, and she has held a commanding average margin of about 40 percentage points in South Carolina, largely on the strength of African American voters, who are expected to make up more than half of the Democratic electorate in the first primary in the South.

Several other Southern states would seem to favor Clinton because of the sizable African American populations, including Arkansas, Georgia, Texas and Virginia. Sanders is simply not known by many black voters.

Aware of such challenges, Sanders has been, and plans to continue, making appearances in several March 1 states, even prior to the first votes being cast in Iowa. On Monday, he drew a crowd of more than 7,000 in Birmingham, Ala.

Stump speeches by GOP presidential candidates reveal that they're already planning for a race against Hillary Clinton in the general election. (Peter Stevenson/The Washington Post)

And while Clinton has buttoned down the support of far more black elected officials, Sanders has his own eclectic set of African American validators showing up at events. They include the flamboyant academic Cornel West, who has praised Sanders for being someone “vanilla” who understands the plight of the “chocolate” community; the Atlanta-based rapper Killer Mike, who has compared Sanders’s agenda with that of Jesus Christ; and Nina Turner, a former Ohio state senator who was a former Clinton supporter.

At an event Monday commemorating the Rev. Martin Luther King Jr. in Columbia, S.C. — where Sanders, who is 74, said he had attended King’s March on Washington in 1963 — Kathleen Tisdale was wearing a Hillary sticker but said she is actually “straddling the fence” between Clinton and Sanders. She said most of her friends, African Americans like her, “are still getting to know him.” But “the little bit they’ve seen, they like,” she added.

“He’s very direct,” said Tisdale, 53, who works for a telephone company. “When he speaks, to me he sounds like a president. He’s got a powerful voice.”

More broadly, Sanders is counting on a shift in momentum that will alter the dynamics in subsequent states if he wins Iowa and New Hampshire. Others agree that it is possible.

“If Sanders beats Clinton in the first two states, there will be a very, very strong narrative about his momentum, and then who knows what happens,” said Mo Elleithee, executive director of the Institute of Politics and Public Service at Georgetown University and a former spokesman for Clinton and the Democratic National Committee.

Elleithee, who is not working for a candidate this year, said Clinton is in a better position to rebound than she was during her 2008 presidential bid, when she finished third in the Iowa caucuses.

“Having said that, I don’t believe there’s a single person in Brooklyn who wants to test that theory,” Elleithee said, referring to Clinton’s headquarters.

Less clear is whether momentum can offset Sanders’s disadvantages — notably in a couple of caucus states where complex rules demand early organization.

In Colorado, where caucuses are scheduled for March 1, the Clinton campaign connected with local party leaders and activists months ago, ahead of the Sanders camp, according to Boulder County Democratic chair Lara Lee Hullinghorst.

Democrats needed to register by Jan. 4 to participate in the state’s March 1 caucuses.

“A lot of Bernie people didn’t know that the 4th was the date, because they were still getting people on the ground here,” Hullinghorst said.

However, she suspects that the flood of new registrations that came in before the deadline may have been roughly split between the two campaigns. “Her proactivity and his passionate base may have balanced themselves out.”

In Nevada, aides say Sanders is stepping up his courtship of Latinos and African Americans as well as his overall ground game.

About 28 percent of the Nevada population is Latino, and 9 percent is black. Both Clinton and Sanders are giving increased attention to the minority vote there.

“A lot of young people are excited, and they will caucus and they will bring their relatives,” said Emilia Pablo, Sanders’s state communications director.

Supporters have also targeted Latinos who will be 18 and eligible to vote by November.

One radio ad in Spanish is focusing on being a first-generation American. The ad says “immigration is not just a word” for Sanders but his “family’s story,” and it talks of his father coming to America from Poland with little money or ability to speak English.

Clinton enjoys high name recognition, and many Latinos in Nevada say they do not know much about Sanders. But many are undecided.

There is also clear disillusionment with President Obama, with many Hispanics feeling that he promised them much in the way of immigration reform and instead deported huge numbers of undocumented immigrants.

Supporters in Nevada hope to capitalize on criticism Clinton received recently for using the term “illegal immigrants.” She later said it was a poor word choice.

Carlos Silva Jr., 49, an immigration activist who works in marketing and consulting in Nevada, said he sees a generational divide among Latinos. The challenge now, Silva said, is getting Latinos to caucus. Many do not understand the process or are working several jobs and don’t have the time to spend on the meetings. But some groups are holding training sessions and mock caucuses to explain it to the many first-time voters.

Sanders has nearly matched Clinton in fundraising during the past two quarters. In the period ending Dec. 31, Sanders said he had raised more than $33 million, just shy of the $37 million that Clinton said she had raised directly into her campaign.

But Sanders’s aides argue they are better positioned because the vast majority of their donors — 99.9 percent, they say — have not given the legal maximum of $2,700. That means they can be tapped again and again. And given that Sanders has amassed more than 1 million individual donors, the campaign sees huge potential.

The Sanders team often points to South Carolina, where Obama trailed Clinton in 2008 polls until after Obama beat her in Iowa.

In this cycle, the vote in South Carolina will be influenced in part by the states ahead of it, said Jamie Harrison, chairman of the South Carolina Democratic Party.

“What happens in Iowa influences New Hampshire, what happens in New Hampshire influences Nevada, and what happens in Nevada influences South Carolina,” he said. “It’s all about momentum and building it.”

Mary Jordan and Philip Rucker contributed to this report.