Gill became a candidate for State Senate in District 34 after some of the municipalities she had represented in the Assembly were shifted into the district. Most of the communities added to District 34, which at the time was a Republican stronghold and had been for nearly two decades prior, were heavily Democratic and contributed to Gill's landslide victory over first-time incumbent Norman M. Robertson. In the 2003 primaries, LeRoy J. Jones, Jr. was given the party line opposing Gill. Despite being outspent by Jones in the heavily Democratic district, Gill won with 55% of the vote. Senator Gill has been re-elected twice, winning elections in 2003 and 2007. Gill, along with the other 39 state senators, was required to run for her seat after two years due to the election cycle set forth in the New Jersey Constitution requiring a two-year Senate term after decennial redistricting.