MEXICO CITY — Vicente Fox spent three years running for president. His first hour in power made it clear that he will have to spend the next six years campaigning as hard as he can to accomplish half of what he has promised.

The hostility that he faced from the old governing party's politicians in a joint session of Congress on Friday as he made his inaugural speech hung in the air like a choking haze. They kept their seats as he entered the room. They sat on their hands as he took the mantle of power.

And as soon as he opened his mouth, talking of dialogue and compromise, they started hooting and jeering. One shouted, "Liar!"

Fox took it in stride. "This is the new reality of power in Mexico," he said Friday. "The force of the nation can no longer come from a single point of view, a single party, a single philosophy."

Now, having taken the presidency from the Institutional Revolutionary Party — until Friday the world's longest-governing political tribe, an inbred clique that corrupted much of what it touched over seven decades — Fox has to use his power to transform the state.

He has an old order to dismantle, a new one to build, and six years to do it.

What he called in his speech "a political culture in which accord has been seen as an act of capitulation" is clearly alive and thriving. But in the streets, hopes are high and rising that Fox can make good his huge promises to create a justice system that does justice, an economy that provides jobs for the poor and middle class, a society liberated from corruption.

Fox says his election signaled not only a popular desire for "political change, a change of party, a change of government," but also "something much more profound, something that emerged from within the heart of each Mexican — overflowing joy, jubilation, hope, expectations, faith, a sense of responsibility and optimism in the future."

That is a lot for one politician to handle alone, especially a one-term governor of a medium-sized state elected with 43 percent of the vote who is facing a divided Congress where the old governing party has a plurality, no side holds a majority and opponents are already throwing stones.

Fox says he will have to tour the nation ceaselessly, campaigning for change, while sleeping in a bungalow on the grounds of the presidential mansion, Los Pinos, not in the presidential suite. Nothing happens in Los Pinos, he says — things happen outside, in the streets of the capital and the cities and villages of Mexico, and that is where he says he wants to be.

He says his goal is to bring jobs, education and security to a country where half the population is poor; where only the richest tenth have a chance to go to college, and the poorest tenth rarely make it past the first grade; where crime, corruption and impunity warp society. He has an increasingly clear sense of where to begin: at the bottom.

Among Fox's first initiatives, he says, will be to create grants to help poor and middle-class people get a college education; micro-credits to help small businesses prosper; and what he calls a "crusade for peace" in the southern state of Chiapas, a bastion of poverty and the seat of a smoldering leftist rebellion. He also has an eye on revising Mexico's laws in the name of reforming the justice system, making the rich — and the poor — pay taxes, and even excavating buried secrets of state.

Fox comes from a party that positions itself to the right of center — pro-business, pro-Catholic, pro-American. But he ran for president on his own, and the party followed. And during that long three-year run, he appeared to straddle the political divide. His appetite for big ideas, his appointments and his promises all suggest a man looking for political convergence — the elusive Third Way, that triangulation of right and left that politicians like President Clinton and the British prime minister, Tony Blair, have sought but not quite realized.

This week, he set in motion a whirl of newly anointed officials charged with remaking Mexico's economy, its relations with the United States, its security apparatus.

He will be the first Mexican leader to approach the United States as a partner, eye-to-eye.