Sharon Runner will face no opposition in the special election for California’s 21st Senate District, as she was the only candidate to file for the seat.

The filing deadline was Friday.

The seat was declared vacant after its previous occupant, Steve Knight, was elected to Congress in November, mid-way through his Senate term.

The district includes the majority of the Santa Clarita Valley as well as the Antelope, Victor and Apple valleys. Southwestern portions of the SCV are represented by Sen. Fran Pavley, a Democrat.

Runner, a 60-year-old Republican from Lancaster, represented portions of the 21st Senate District in 2011 and 2012 when it was differently numbered and configured. From 2002 to 2008 she served in the state Assembly.

Runner was a driving force behind the passage of Proposition 83 in 2006, the California version of Jessica’s Law. It increased the penalties for sex offenders and reclassified certain crimes as sexual offenses.

The last time Sharon Runner was elected to the Senate, it was to complete the unexpired term of another person who had been elected to higher office – her husband, George Runner, who was elected to the state Board of Equalization.

Two years later, in 2012, Sharon Runner opted not to seek a full Senate term after learning she would need a double lung transplant. She had been diagnosed with limited scleroderma, an autoimmune disease that attacks the body’s healthy tissue and organs.

She had the transplant in early 2012.

“We are thrilled with Sharon’s rapid progress,” her doctor, David Ross, Medical Director of the Lung and Heart-Lung Transplant Program at UCLA, said at the time. “Her new lungs will enable her to resume normal activities and responsibilities soon.”

Runner said her recovery is complete and she’s ready to return to Sacramento to “combat the job-killing over-regulation, over-taxation and the dangerous situation created by early release of felons by Prop. 47 and realignment.”

Earlier this month, Gov. Jerry Brown set a date of May 19 for the special election, following a March 17 primary. The special election was to follow California’s “top two” procedure, but that appears to be moot at this point.

Several names had been tossed around in recent weeks as potential candidates, but most ended up endorsing Runner’s bid, including Palmdale Mayor Jim Ledford, Lancaster Mayor R. Rex Parris, Hesperia Mayor Eric Schmidt, Lancaster Vice Mayor Marvin Crist and Santa Clarita Councilman Dante Acosta, who is also a field deputy to Knight.

Late last week two Democrats who had previously sought the seat – Darren Parker, who lost to Runner in 2010, and Star Moffatt, who lost to Knight in 2012 – publicly announced their decision not to run.

A onetime Realtor, Sharon Runner founded Desert Christian Schools with her husband in 1977. She volunteered on numerous community and business boards, and her first political position came in 1998 when then-Gov. Pete Wilson appointed her to the Antelope Valley Fair board.