Sanders scored a big victory in the Nevada caucuses, strengthening his position as the front-runner for the Democratic nomination

Senator Bernie Sanders of Vermont won the Nevada caucuses. He dominated the contest by assembling a multiracial coalition that brought his long-promised political revolution to life.

Former Vice President Joseph R. Biden Jr., former Mayor Pete Buttigieg of South Bend, Ind., and Senator Elizabeth Warren of Massachusetts finished well behind Mr. Sanders, according to early results. The hedge fund billionaire Tom Steyer, Senator Amy Klobuchar of Minnesota and Representative Tulsi Gabbard of Hawaii were at the back of the pack. Michael R. Bloomberg, the former mayor of New York, was not contesting Nevada.

Despite scattered reports of volunteer shortfalls and busy phone lines, the caucuses appear to have run relatively smoothly. The Nevada Democratic Party was slow to release results.