Pennsylvania's 12th Congressional district goes from leans Republican to toss-up

Rep. Keith Rothfus was first elected to Congress in 2010, represented the 4th congressional district.   Redistricting moved him into a much realigned 12th district.

Source:  Ballotpedia 

The art of the Pennsylvania gerrymander

Source:  govtrack

The new map for the 2018 election

Not  a flippable seat, strictly speaking.  More like a whole new ballgame.

Other flippables:
Martha McSally, Arizona 2nd.  (10/8/2017)
Jeff Denham, California 10th.  (10/9/2017)
David Valadao, California 21st.   (10/10/2017)
Steve Knight, California 25th.  (10/11/2017)
Ed Royce, California 29th.  (10/12/2017)
Mimi Walters, California 45th CD.  (2/12/2018)
Brian Mast, Florida 18th.  (10/13/2017)
Carlos Curbelo, Florida 26th.  (10/14/2017)
Mike Bost, Illinois 12th. (10/15/2017)
Rod Blum, Iowa 1st CD.  (2/12/2018)
Kevin Yoder, Kansas 3rd.  (10/16/2017)
Andy Barr, Kentucky 6th CD.  (2/12/2018)
Mike Bishop, Michigan 8th CD.  (2/12/2018)
Erik Paulsen, Minnesota 3rd.  (10/17/2017)
Don Bacon, Nebraska 2nd.  (10/18/2017)
Tom MacArthur, New Jersey 3rd.  (10/19/2017)
Leonard Lance, New Jersey 7th.  (2/14/201)
Lee Zeldin, New York 1st CD.  (2/12/2018)
John Faso, New York 19th CD.  (2/12/2018)
Claudia Tenney, New York 22nd.  (10/21/2017)
John Katko, New York 24th CD.  (2/12/2018)
Steve Chabot, Ohio 1st CD. (2/12/2018)
Ryan Costello, Pennsylvania 6th.  (10/23/2017)