Catchword (noun)

1. A phrase or expression that is popular and widely used, especially one that has become a cliché.
2. A word or phrase repeated often by someone to express a particular attitude or view.

Origin:

Late 16th century: from catch + word.

Examples:

1. The catchword of his campaign was 'Change We Can Believe In'.
2. She became known for her catchword, 'You go, girl!'.
3. The catchword among economists is that inflation is a serious problem.
4. His speeches were full of catchwords and cliches.
5. The catchword of the party was 'Freedom and Equality'.