Tai, 53, will fill the last six months of the term of former State Rep. Scott Petri (R., Bucks), who left in January to become executive director of the Philadelphia Parking Authority. During that time, the new representative and Thomas will continue to campaign against each other to try to win a full two-year term on Nov. 6.
Republicans have held the central Bucks district for 34 years.
A Solebury Township supervisor, Tai will be the 42nd woman in the state House, the highest number of female members the chamber has had at any one time, according to Bill Patton, spokesman for the Democratic caucus. Democratic National Committee Chairman Tom Perez acknowledged Tai's accomplishment in a statement late Tuesday, saying "the wind is at our backs" in Pennsylvania.
EMILY's List, a national political committee that backs Democratic women who support abortion rights, also hailed Tai.
Thomas, 57, of Northampton, is a health-care executive who resigned from her position on the Council Rock school board to run for the legislative seat.