What is the threshold issue in the anti-SLAPP context?

In terms of the so-called threshold issue, the moving party's burden is to show "the challenged cause of action arises from protected activity." (Rusheen v. Cohen (2006) 37 Cal.4th 1048, 1056.) "[T]he statutory phrase 'cause of action . . . arising from' means simply that the defendant's act underlying the plaintiff's cause of action must itself have been an act in furtherance of the right of petition or free speech. [Citation.] In the anti-SLAPP context, the critical point is whether the plaintiff's cause of action itself was based on an act in furtherance of the defendant's right of petition or free speech. [Citations.] 'A defendant meets this burden by demonstrating that the act underlying the plaintiff's cause [of action] fits one of the categories spelled out in section 425.16, subdivision (e) . . . .'" (City of Cotati v. Cashman (2002) 29 Cal.4th 69, 78.)