Because it's in the news today, here's a reminder about how we have defined the word "plagiarism":
"Taking someone else's work and intentionally presenting it as if it is your own."
Note the word "intentionally."
We can talk about phrases that are "word-for-word" or that "mirror each other." It's fine to say there's a "plagiarism issue" or that the speech last night raised questions about whether some parts were plagiarized. But we don't know at this time whether anything was done "intentionally." So don't declare that there's been some plagiarism.