At the 1722, Waller stood for Parliament at Wycombe, where his family had a major interest and also at St Ives but was unsuccessful at both. He stood for Wycombe at a by-election on 1 February 1726, which was declared void after irregularities. After a second by-election on 3 March 1726, he was returned on petition as Member of Parliament for Wycombe on 17 March. The mayor responsible for the management of the elections was committed to Newgate as a result. Waller was returned unopposed at the 1727, 1734 and 1741 general elections, and was returned with his brother Edmund in 1734 and after.[1]
After the fall of Walpole in 1742, Waller followed his elder brother Edmund into opposition and voted consistently against the ministry. However, Edmund took office under the Government as Cofferer of the Household in 1744, whereupon Harry was considered a ‘New Ally’ for the Government. Harry retained his seat until the 1747 general election, when he stood down in favour of his nephew, Edmund Waller junior.[1]