He fought Lewisham East in the February 1974 general election, coming second to Labour's Roland Moyle.
Both MPs put a great deal of effort into the fight, hiring minibuses to ensure all their supporters got to the selection meeting; the contest became bitter when Booth accused Marshall of "signing up the dead and the dying" as Conservative members in order to boost his chances of victory.
Despite most of the new constituency coming from Booth's old seat, Marshall won the selection contest on 1 November 1995, but went on to lose the contest for the seat to the Labour Party candidate Rudi Vis at the 1997 general election, in which the Conservatives experienced their worst electoral defeat in 91 years.
Notable losses included Portillo, who Marshall had lost to in the Conservative selection for the Enfield Southgate by-election thirteen years earlier, along with several cabinet ministers.
He unsuccessfully sought to regain his Finchley and Golders Green seat at the 2001 general election, but Labour's Rudi Vis beat him by 3,716 votes.