MEXICO CITY, DEC. 30 -- The man who is almost certain to be Mexico's next president is attempting to wage a more open campaign than is the tradition here, where the ruling party has never lost. But he is facing resistance from within his party and strong attacks from an opposition emboldened by the country's worsening economic troubles.

Former budget minister Carlos Salinas de Gortari, designated as the 1988 presidential candidate of the ruling Institutional Revolutionary Party, or PRI, almost three months ago, has publicly condemned vote fraud and warned party regulars that the PRI can no longer expect to triumph "in every election everywhere."

Since its founding 58 years ago, the PRI has never lost a federal or state election, but in the past five years opponents have gained strength throughout the north and in scattered urban districts to the south.

In another break with the past, Salinas has issued what subordinates say are strict orders against the use of government funds and facilities in the presidential contest. But aides acknowledge that his orders have not always been strictly enforced, and the opposition has been quick to point this out.

"We are not running against another party here, we are confronting the entire apparatus of the state," Esteban Zamora, a leader of the conservative National Action Party, or PAN, in the state of Sinaloa said recently. As he spoke, he surveyed a hotel lobby crowded with press and staff members attached to Salinas' campaign during a stop there.

Nevertheless, PRI rallies have been modestly scaled in comparison to past extravaganzas leading up to the vote on July 6. Instead, the candidate's energies have been focused on radio talk shows, question-and-answer sessions with critics and labor and industry groups and unrehearsed encounters with voters in the street.

Interrupting the normally rigid itinerary of a PRI campaign tour, Salinas has made surprise visits to Chihuahua, another opposition stronghold, and to the border gulch separating Tijuana from California, where he spoke with would-be undocumented emigrants about their charges of abusive treatment by corrupt local police.

Salinas readily acknowledges that his pleas for greater democracy have had a "mixed reception" within party ranks.

"There is always internal resistance when traditions are broken," Salinas said in a conversation with foreign reporters on his comfortably appointed campaign bus. "There are ideas that are received well as ideas, but that are still difficult to convert into realities."

A 39-year-old economist with three Harvard postgraduate degrees, Salinas is saddled with an image as a bookish technocrat, skilled in budget policy but lacking political experience. Yet he was raised in an intensely political household -- his father was a Cabinet minister and one-time presidential aspirant -- and he acquired hands-on training as manager of President Miguel de la Madrid's 1982 campaign.

On the campaign circuit, Salinas seems invigorated by the grueling routine of speechmaking, handshaking and closed-door gripe sessions with provincial elites. Aides recognize that Salinas is far less effective at the hortatory rhetoric that typifies PRI electioneering.

By replacing mass rallies with more intimate campaign meetings, they say they hope to exploit the talents of a candidate who even critics acknowledge is well-informed about local political and economic problems.

This strategy of "dialogue" -- of "letting Mexico speak," as the official campaign slogan puts it -- has not been universally welcomed within ruling party ranks. In the southern border state of Chiapas last month, for example, Salinas held discussions with a dissident "democratizing" faction of the huge PRI-affiliated teachers' union, angering the union leaders whose autocratic organization is still a central component of the party's electoral machinery.

"Salinas is making a genuine effort to have a different, more direct kind of interchange with local pressure groups, but it remains to be seen whether the effort is succeeding," a European diplomat commented. "First, no matter how hard you try, it is difficult to change the staged nature of these proceedings. Secondly, you can get into trouble with the local bosses on whom the PRI ultimately still depends. And finally, it is an open question whether Salinas has the presence -- the force of personality -- to convince a cynical public that he really does stand for change."

Even without the use of public funds, the PRI's resources are overwhelmingly greater than those of all rivals combined. Government bureaucrats finance the campaign with mandatory paycheck deductions, while industrialists curry favor by donating fleets of buses and planes. Moreover, with five registered opponents dividing the opposition on the right and left, Salinas is virtually guaranteed a solid plurality, the candidate and his aides acknowledged.

Yet they expressed "real concern" about opposition inroads in congressional elections, advances they say come largely from the PRI's growing difficulty in getting out the progovernment vote. Once used to landslide majorities in contests with 80 percent of the voters participating, the PRI has recently been winning state and local votes with far smaller margins in turnouts as low as 25 percent.

"We are facing a serious problem of voter abstention," Salinas said. "But to the extent that we can make the election process more . . . trusted by people, I am sure that more will vote."

The opposition is also finding it harder to get voters to the polls, in part because of its repeated accusations that the PRI fraudulently fixes election results, professionals from both sides say.

The PAN, Mexico's biggest opposition party, was officially credited with 17 percent of the vote in the 1982 election and is expected by the PRI to improve its showing this time. In Sinaloa, as in other relatively affluent northern states, the PAN's support approaches a majority in major cities, threatening the PRI with embarrassing mayoral and legislative losses.

The PAN's standard bearer is Manuel Clouthier, a wealthy Sinaloa tomato grower and 1986 gubernatorial challenger. Combative and blunt-spoken, Clouthier has lashed out at the PRI for "monopolizing power behind the people's backs for more than half a century."

In the past two months, Mexico's economy has taken a drastic turn for the worse, with the stock market crashing and the peso tumbling against the dollar. To cut its deficit and brake inflation -- expected to hit 150 percent this year, far above 1986's record 106 percent -- the government has imposed unpopular new austerity measures.

These economic troubles have given new life to the opposition, political professionals say. Candidates of the right and left are leading street protests against the new austerity policies, while Salinas is constantly buttonholed by ordinary voters demanding to know how the government will lower food prices and provide jobs to the unemployed young.