Is there a restraining power at work today keeping the Antichrist from appearing?
Yes. A restraining power is actively at work on the earth today, withholding the Antichrist so he cannot be revealed until God's time. It functions like a dam in a river, preventing him from appearing on the scene ahead of schedule.
Les explains from verse 6 that Paul writes, "you know who withholdeth or restraineth," comparing this restraint to a dam in a river. The purpose is that the Antichrist might be revealed in his time, not ahead of time. Les emphasizes that there is a restraining power on the earth tonight making sure the man Antichrist does not come on the scene until it is God's time. He also stresses why prophecy is important for believers, especially as we approach the hour.