Heftye served one term in Kristiania city council, from 1907 to 1910. On 19 March 1908, when the Knudsen's First Cabinet assumed office, he was appointed for his second term as Minister of Defence. He resigned already on 10 April the same year, because Prime Minister Gunnar Knudsen refused to seek a vote of confidence in Parliament, a form of investiture. This was a problematic question at that time, as Norway had made important steps towards parliamentarism, but not formalized the process with change of government. Former Prime Minister Christian Michelsen had asked for a vote of confidence following the 1906 general election, and survived. When he retired from politics in 1907 due to illness, Jørgen Løvland took over, but he was felled in 1908. In early 1908, the Liberal Party had evicted 24 legislators who supported Christian Michelsen and the endeavors of the Coalition Party (later leading to the creation of the Liberal Left Party), and hence, when Knudsen took over, he had no way of achieving a parliamentary majority. In that situation he could not expect to survive a vote of confidence. On the other hand, Knudsen and his cabinet resigned following the 1909 general election, which the Liberal Party lost. Such an action is not required by law, but if not carried through, the cabinet would most likely face a vote of no confidence.