Danielle Smith + 8 Wildrose MLAs

On December 17, 2014, Wildrose Party leader Danielle Smith led nine of the party's seventeen MLAs across the floor of the Alberta Legislature to join the governing Progressive Conservative Party under Premier Jim Prentice. The mass crossing — the largest in Alberta history — stunned supporters who had backed Smith as the face of conservative renewal against the PC dynasty. Smith argued that Prentice had adopted enough Wildrose policies to make a separate party unnecessary, and that a "united conservative movement" would be stronger. The eight MLAs who joined her were Rob Anderson (who had previously crossed from PC to Wildrose in 2010), Gary Bikman, Rod Fox, Jason Hale, Bruce McAllister, Blake Pedersen, Bruce Rowe, and Jeff Wilson.

The mass crossing backfired catastrophically. Wildrose voters felt profoundly betrayed; PC supporters viewed the newcomers with suspicion. Smith lost her PC nomination for Highwood in a party vote just months later, humiliated by the same grassroots activists she had tried to join. In the May 2015 Alberta election, Rachel Notley's NDP swept to a shock majority government, ending 44 years of PC rule. Many analysts credited the Wildrose crossing with fatally fracturing the Alberta conservative vote and enabling the NDP victory. It became the textbook example of a floor crossing that destroyed both the crosser and the party they crossed to.