Watson was appointed the second chair of the Electoral Commission in January 2009. She was paid £100,000 for a role which required her to work three days a week. Watson remained chair of the electoral commission amidst criticism of her management of the 2010 United Kingdom general election, when she defended herself on the grounds that the Electoral Commission had few powers over returning officers. Since then, the Parliamentary Voting System and Constituencies Act 2011 has increased the Commission's authority with regard to referendums. She formally announced the results of the Welsh devolution referendum "in both English and Welsh with perfect pronunciation". Just two months later, she acted as Chief Counting Officer (CCO) in the 2011 AV Referendum and also acted in the same capacity in the 2016 EU Referendum. In doing so, she became the first person to oversee two UK-wide referendums as Chief Counting Officer.