Fine. Find your pure candidate that has never changed an opinion or position in his entire political career, and then support him as long as he is in the race. But you need to consider what you will do when he is no longer a candidate - will you support another who may have changed their position on some issues, or will you decline to support anyone?
This is not about purity. This is about winning. Flip-flopping does not engender trust but the opposite. When political expediency trumps conservatism, you might as well vote Dem.