In its early years the party was divided between abstentionists and anti-abstentionists. The abstentionists would immediately resign their post in the Council of Government immediately upon election as a protest against the token representation of the electorate on the Council; the anti-abstentionists favoured co-operation with the colonial authorities in order to work for a better constitution.
Following the First World War a broader and more moderate coalition, the Maltese Political Union (UPM), was formed but a more radical and pro-Italian group, the Democratic Nationalist Party (PDN), split from the main party. The two groups contested the first legislative elections of 1921 separately as they did in the following elections in 1923. In both legislatures the government was led by the UPM, first in coalition with Labour and then in coalition with the UPM.
The wo parties formally merged in 1926 as the Nationalist Party. It lost the 1927 election to the Compact (an alliance between the Constitutional Party and Labour). A constitutional crisis, resulting from a dispute between the Church and the Constitutional Party, meant that elections were suspended in 1930. They were held again in 1933 when the Church interdiction on the Constitutional Party and Labour meant that the Nationalists won by a landslide (21 seats out of 32). However, the Nationalists did not last long in government. The colonial authorities, concerned at the rise of fascist Italy in the Mediterranean and Africa, suspended the government and the constitution on the pretext that government's measures to strengthen instruction of Italian in schools violated the Constitution.
The Nationalists received what could have been their coup de grace during the War. There association with Italy antagonised them with the electorate and their leader, Dr Enrico Mizzi (son of Fortunato) was first interned and then exiled to Uganda during the War.
In the first post-War legislative elections held in 1947 the various splinters appeared formed by people who did not want to associated with the main party. The party managed only 18% in those elections but it stayed ahead of the other splinters which soon disintegrated. In fact, thanks to a split in the Labour Party, the Nationalists emerged as the largest party in the 1950 elections and formed a minority government.
A number of elections were held and short-lived coalitions were formed with the Malta Workers Party (a moderate splinter of the Labour Party) in the early 1950s until the party went into Opposition in 1955. During that time the party led the campaign against Integration with Britain, a proposal that subsequently failed, until the Constitution was again revoked in 1958 following massive disturbances.
A new Constitution was enacted in 1961. The party won the 1962 elections which were fought largely over the issue of independence and a second politico-religious crisis this time between the Church and the Labour Party. Independence was achieved in 1964 and the party was returned to office in 1966. It lost the 1971 elections with a narrow margin and lost again in 1976.
In the elections of 1981 the party achieved an absolute majority of votes for the first time since 1933 but did not gain a parliamentary majority and was relegated to the opposition. A crisis followed with the party MPs refusing to take their seats seeing they were kept out of office due to gerrymandering. Amendments to the constitution in 1987 meant that the party was voted into office that same year.
In 1990 the government formally applied to join the European Community. A wide-raging programme of liberalisation and public investments meant the return to office with a larger majority in 1992. However, an unpopular tax saw the defeat of the party in the 1996 elections. The stint in opposition would last only 22 months as the government soon lost its one-seat majority. The party won convincingly the 1998 elections, a feat that was repeated in 2003 following the conclusions of accession negotiations with the European Union in 2002.
The party presently holds 35 seats in the 65 member House of Representatives. It is led by Dr Edward Fenech-Adami.