Campaigning was halted but Aznar insisted the elections would proceed.
"No fanatical minority will take away ... the free decision of Spanish citizens," Aznar said Friday.
His party presided over an economic upswing in the 1990s marked by lower taxes and a balanced national budget.
Before the attacks, polls unanimously gave the Popular Party a clear advantage but cast doubt over whether it would retain a majority in the 350-seat Parliament.
Aznar's party currently holds 183 seats.
Aznar, who survived a 1995 car bomb assassination attempt by ETA, has made the fight against terrorism and specifically ETA one of the main policies of his eight years in office.
Also, the opposition Socialist candidate was embarrassed last month by revelations that a coalition partner in the Socialist-led government of Catalonia, a wealthy northeast region where separatist fervor runs strung, secretly met with ETA members in France.
That violated a pact among major parties barring talks with the group, and the Socialists were accused of undermining Spain's fight against ETA.
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