I agree with you, but I do wonder how much of that is just because they're just looking at short-term effects ("how many votes can I swing over the next 6 months"). Major changes to a person's belief system (or to a borderline tribal identity like political parties can be) can happen, but they usually happen over years or decades, not weeks or months.

Edit: Although I should mention that a person's parents political view tend to be a fairly good predictor of your political party affiliation, so perhaps even the long-term effects are moderate at best.