Senator Bernie Sanders (I-Vt.) made waves as a democratic socialist presidential candidate. Here's what you need to know about being a democratic socialist and how it's different from socialism. (Alice Li/The Washington Post)

IOWA CITY, Iowa -- Presidential hopeful Bernie Sanders said Sunday that he is preparing to give a “major speech” on democratic socialism, the political philosophy that is guiding him and his upstart campaign for the Democratic presidential nomination.

“I think we have some explaining and work to do,” the Vermont senator told an audience at a house party here in the nation’s first caucus state, acknowledging that the term “democratic socialism” makes some people “very, very nervous.”

Sanders, an independent who caucuses with Democrats in the Senate, has long identified as a democratic socialist. As a presidential candidate, he has put forward policies that try to create more fairness in a country he says is now rigged to favor the rich -- but he has stopped short of calling for classic socialist ideas, like government takeovers of private industry.

[What is a democratic socialist? Bernie Sanders tries to redefine the name.]

Sanders, for instance, has advocated free tuition at public colleges and universities, a single-payer health-care system, guaranteed family leave for workers and a “massive” federal jobs program to put more people to work and to fix the country’s infrastructure.

Sanders said his speech on democratic socialism is one of several addresses his campaign is preparing as his race against Hillary Rodham Clinton heads toward the first nominating contests early next year.

Aides said there is no date set yet for the speech on democratic socialism.

On a two-day swing through Iowa that began Sunday, Sanders also pressed a plan to revamp the way Social Security cost-of-living increases are calculated. Sanders bemoaned last week's Social Security Administration announcement that it would freeze retirement benefits next year, barring action by Congress.

[Bad news for retirees: No Social Security cost-of-living increase]

“I myself think it’s an outrage,” Sanders said. “This is an issue we’re going to stay on.”

Sanders has proposed using criteria more specific to seniors -- such as prescription drug costs -- to gauge the need for such increases, rather than making a determination based on a broader measure of inflation.

Sanders has also called for a broader expansion of Social Security benefits that would be paid for “scrapping the cap” on payroll taxes for those with incomes above $250,000.

Sanders’s swing through Iowa also had some lighter moments. He was asked about actor Larry David's portrayal of him on Saturday Night Live. David, among other things, suggested the democratic socialist wears only one pair of underwear.

Sanders assured reporters that he has “an ample supply.”