gardner was a sitting congressman who ran for the senate with a platform of fiscal conservatism, to get rid of obumbercare and to fix illegal immigration. After he won, before he left the house, he voted to fund obumbercare for two years, supported obumbers massive spending initiatives and voted for boehner who was staunchly supportive of illegal immigration.
Gardner has voted the “Trump line” 89.1% of the time.
https://projects.fivethirtyeight.com/congress-trump-score/cory-gardner/
There are some higher scores, but 89.1% is pretty decent.
Collins by contrast is at 67%