A new coalition of political outsiders that energized municipal politics here made Federico Pena the Mile High City's first Hispanic mayor.

Pena, 36, a former state legislator, got 79,453 votes, or 51.4 percent, to defeat former district attorney Dale Tooley, 49, who got 75,043 votes, or 48.6 percent. Officials said Tuesday's 71.4 percent voter turnout--electing the first new mayor in 14 years--was the heaviest in the city's history.

On historic Larimer Street, young people cruised their cars slowly Tuesday night, shouting "Chicano Power!"

"This entire process . . . was a credit to Denver," said Tooley, a native of the city, after losing his third mayoral bid. He promised to support Pena's administration with "high enthusiasm."

Pena, who takes office July 1, said the civility he and Tooley displayed "created a new standard in politics." Also, Pena said, "Denver is not Chicago. Race was never an issue, and the people of Denver must be proud of that."

Pena's victory was the latest example of Hispanic gains in urban power. Maurice Ferre has been mayor in Miami since 1973, Bob Martinez in Tampa since 1979, Henry Cisneros in San Antonio since 1981 and Louis Montano in Santa Fe since 1982.

Pena built a potent political organization based on young newcomers who never felt included in local elections, on blacks and Hispanics who in the past did not bother to register and on voters who hitherto had not cared much about city elections. Together they make up about 40 percent of the electorate.

Since both candidates are liberal Democrats who agree on most issues, the five-week runoff campaign was a contrast of styles and strategy. It focused on crime, pollution and where to locate a new airport.

Tooley, who ran unsuccessfuly against incumbent Mayor William McNichols in 1971 and 1975, contended that his 10 years in city government gave him an understanding of how it works and demonstrated his management ability.

Pena, the son of a Brownsville, Tex., cotton broker, moved to Denver in 1972, and as a young lawyer fought for Mexican-American educational rights. As a state representative he helped write the nation's first law requiring many school districts to offer courses in Spanish language and Hispanic culture.

His campaign headquarters was manned by dozens of young professionals, many of them new to politics, who did the telephone canvassing and fund-raising.

After the May 17 primary, about 6,000 new voters registered. City officials said that most told them they wanted to vote for Pena and some said they wanted to join the "Pena party."

Pena finished first in the primary with 36 percent of the vote compared with 30.5 percent for Tooley. McNichols, 73, who was seeking a third four-year term, finished a distant third with 19 percent.

Under McNichols, whose family has been prominent in Denver politics for 60 years, a building boom crowded downtown with stark towers of reflective glass and steel. Yet Mayor Bill, as he is known, was seldom credited for it. Instead, voters complained of cronyism, an absence of planning and an unimaginative style.

Recognizing that McNichols had won in the past because of low turnout and lack of interest, Pena set out to run a campaign that would attract non-registrants to the polling booth.

"There was a tenacity in the minority community that we just haven't witnessed before," said Monte Pascoe, a white liberal who also ran in the primary.