The Panama held a general election on 10 May 1964, electing both a new President of the Republic and a new National Assembly. 7 candidates competed in the 1964 presidential elections, although only three were serious contenders. Marco Aurelio Robles, who had served as minister of the presidency in Roberto F. Chiari's cabinet, was the candidate of the National Opposition Union, comprising the PLN and 7 smaller parties. After lengthy backstage maneuvers, Robles was endorsed by the outgoing president. Juan de Arco Galindo, a former member of the National Assembly and public works minister and brother-in-law of former President Ernesto de la Guardia, was the candidate of the National Opposition Union coalition, comprising 6 parties headed by the CPN. Arnulfo Arias was supported by the PP, already the largest single party in the country. "PLN retained the presidency in 1964 when Robles won 134,627 votes compared with 123,186 for Arias, now candidate of the Panamanian Party. Arias maintained that the elections had been rigged and demanded a recount, but the National Elections Board upheld the result".
"As the 1968 elections approached the opposition accused President Robles of unlawfully using his office to support the candidacy of David Samudio as his successor. The opposition parties held a majority in the legislature, which impeached Robles". The National Assembly met in special session and appointed a commission to gather evidence. Robles, in turn, obtained a judgment from a Municipal Court that the Assembly was acting unconstitutionally. The National Assembly chose to ignore a stay order issued by the municipal court pending the reconvening of the Supreme Court on 1 April, and on 14 March it voted for impeachment. On 24 March, the National Assembly found Robles guilty and declared him deposed and replaced him with Max Delvalle, who being the senior Vice-President was sworn in as President of the Republic. Robles and the National Guard ignored the proceedings, maintaining that they would abide by the decision of the Supreme Court when it reconvened. The Supreme Court, with only one dissenting vote, ruled the impeachment proceedings unconstitutional. But Delvalle denied its authority to overrule decisions of the legislature and continued to fill the presidency. The Electoral Tribunal subsequently ruled that thirty of the parliamentary deputies involved in the impeachment proceedings were ineligible for reelection. Robles, with the support of the National Guard, retained the presidency.
