The 1828 Clare by-election was notable as this was the first time since the reformation that an openly Roman Catholic MP, Daniel O'Connell was elected.

However, under the Oath of Supremacy required of MPs to take their seats, Catholics were not permitted to sit in the House of Commons of the United Kingdom.

Clare was held by William Vesey Fitzgerald when he was appointed as President of the Board of Trade.

O'Connell won the by-election, but could not take the Oath of Supremacy, which was incompatible with Catholicism and so could not take his seat in parliament.

The Prime Minister, the Duke of Wellington, and the Home Secretary, Sir Robert Peel, who had previously opposed Catholic participation in Parliament, saw that denying O'Connell his seat would cause outrage and could lead to another rebellion or uprising in Ireland, which was about 85% Catholic.