With the congressional palace in La Paz besieged by demonstrators, Hormando Vaca Díez, president of the Senate, has called on the legislature to convene on Thursday. Congress will vote on whether to accept President Carlos Mesa's offer on Monday night to step down.

According to the constitution, Mr Vaca Díez is next in line. Should he refuse the presidency, it would pass to the head of the lower house and then to Eduardo Rodríguez, president of the Supreme Court, who would call new elections.

In a poll by the Apoyo organisation, 55 per cent of respondents said they would support Mr Rodríguez and fresh elections, while only 16 per cent backed Mr Vaca Díez to serve out the rest of the presidential term, which ends in 2007.

And apparently one of those calling for new elections is outgoing President Carlos Mesa:

On Tuesday night Mr Mesa begged Mr Vaca Díez to allow fresh elections. After a day in which police clashed with thousands of protesters in central La Paz, the president said: “The only way to avoid further violence is to hold elections.”

Despite his official reluctance, indications suggest Mr Vaca Díez might take the job. This has alarmed the left; the congressional leader is a landowner from Santa Cruz, the south-eastern region where business leaders are politically powerful, foreign energy companies are based, and which has a strong autonomist movement.

A consummate political operator, Mr Vaca Díez, who represents for many the discredited traditional political parties, looks to have the support of a congressional majority, the armed forces, and possibly Washington. He has shown leadership by signing into law a controversial hydrocarbons bill that Mr Mesa refused to touch.

Mr Mesa, whose predecessor had to flee after sending troops against protesters, has resisted using force against the demonstrations. Mr Vaca D´ez might be more likely to do so. “The country is on the verge of civil war,” Mr Mesa warned on Tuesday night.

La tension se siente.