Onslow worked assiduously to improve his estate, and his situation improved again when Foote died in 1688; his estate was divided between Mary and Sarah, and Denzil's income rose to £2,000 a year. As his fortunes and social status rose, Onslow began to cultivate political ambitions. He found his opportunity in the
Exclusion crisis in 1679 which was an attempt before the successful attempt to dethrone
James II of England. Standing as a pro-Exclusion Whig, he was returned as
Member of Parliament for the borough of
Haslemere. In 1689, in the aftermath of the
Glorious Revolution, he recovered his seat at Haslemere. Onslow's political activity is not readily traced; his nephew
Foot Onslow seems to have taken a greater part in Parliamentary affairs. He supported
Sacheverell's clause excluding from office members of municipal corporations that had surrendered their charters to
James II; however, during 1693 and 1694, some observers considered him an adherent of the
Court party. In 1695, he stood alongside his nephew Sir Richard to become a knight of the shire (MP) for Surrey, narrowly eking out a victory over
Edward Harvey (which Harvey unsuccessfully appealed to the committee of privileges). Thereafter his votes stamped him as a solid Whig, although his attendance in Parliament was desultory. At the next election in 1698, the Onslow interest was suffering from a scandal: his nephew Foot's electioneering at Guildford after which the family did not dare attempt to monopolize the two seats for Surrey as a whole. He did not return to Parliament until February 1701 in a by-election for Guildford, where Foot had resigned to become an
excise officer. ==Difficult years==