Any examples you'd like to bring up? It's far more common for politicians to claim to be progressive up until the point of assuming office, only to revert to status-quo business as usual afterwards. Obama is the most famous recent example that comes to mind. Ending wars, closing Guantanamo, restraining police state spying, making college more affordable, and implementing socialized healthcare were all campaign agenda items of his that were never achieved even when his party had a super-majority (most never even mentioned again once he was in office).