Why does Hillary Clinton tend to under-perform expectations?

[IceSpear]

She didn't in NY. Lazio was supposed to make it a close race and he got crushed. She won by a huge margin in 06 too despite being "polarizing" and yadda yadda.

As for the presidential years, it's a few things. For one, Obama and Sanders (particularly Obama) were much stronger competitors than most gave them credit for, so it has as much to do with them exceeding expectations as Hillary underperforming them. The media also relentlessly goes after her and peddles faux scandals while she's on the national stage due to multiple factors (sexism, ratings, wanting a horse race, etc.) The media and politics abhors a vacuum. Sweeping all 50 states was never going to happen.

[IceSpear]

She still under-performed expectations though she only won 55-43 against a relatively weak challenger while Gore won NY 60-35. That was the only competitive election she has won in her entire career.

That's revisionist history. Lazio was pumped up as a strong challenger and the race was characterized as a barnburner that would go down to the wire.