From the replays I saw, Smith did have a nose under Stewart when Stewart threw that block. I thought it was pretty conclusive that Smith was forced down under the line. If Smith doesn't go below the line, he takes out Stewart and a bunch of other cars and possibly himself as well.

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"Why do so many people need help? Life's not that complicated. You get up, go to work, eat three meals, take one good s***, and go back to bed. What's the f***ing mystery?" - George Carlin - Complaints & Grievances