MADRID, June 13 -- Spain's conservative opposition has spent weeks insisting that Pedro Sanchez's government is finished, drowning in corruption cases and abandoned by the public. This week its leader put a number on the claim: 184 members of parliament, he said, want immediate elections. The trouble is that the number that matters is 176, and he cannot reach it.

Alberto Nunez Feijoo, who leads the People's Party, has been testing the ground for a motion of no confidence against the Socialist prime minister, the parliamentary mechanism that could in theory force Sanchez out and trigger a vote. On Monday he claimed a majority of the 350-seat Congress now wanted the government gone, a tally that included the seats held by the far-right Vox...