The Democratic Congressional Campaign Committee on Tuesday began a $500,000 advertising campaign on television and online tying eight House Republicans, including Representative Kevin McCarthy of California, the minority leader, to Ms. Greene and QAnon, an effort to force them to make a public affirmation about Ms. Greene.

“Congressman Don Bacon,” an ominous-sounding voice intones in the ad targeting the Nebraska Republican, “he stood with Q, not you.”

The strategy is similar to the one Republicans employed against Democrats last summer during the protests over racial injustice, when they sought to paint all Democrats as in favor of defunding the police, including President Biden, who repeatedly said he did not favor it.