LA PAZ, Bolivia — Rodrigo Paz, a centrist senator who was never a nationally prominent figure until now, won Bolivia's presidential election on Sunday, preliminary results showed, galvanizing voters outraged by the country's economic crisis and frustrated after 20 years of rule by the Movement Toward Socialism party.

"The trend is irreversible," Óscar Hassenteufel, the president of the Supreme Electoral Tribunal, said of Paz's lead over his rival, former right-wing President Jorge "Tuto" Quiroga.

Paz won 54% of the votes, early results showed, versus Quiroga's 45%.

Paz took the podium Sunday night flanked by his wife, María Helena Urquidi, and four adult children. The hotel ballroom in Bolivia's capital of La Paz went wild, with people shouting his name and holding phones aloft.

"Today

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