Question: What might be included in the “strong delusion” in 2 Thessalonians:2:11And for this cause God shall send them strong delusion, that they should believe a lie:
See All... [1]? And is it already here, or does it only take effect after the Rapture?

Response: Paul says that the “delusion” specifically causes those who “received not the love of the truth” to be deceived by the “lying wonders” performed by Antichrist [2] (“that Wicked...whose coming is after the working of Satan”) and by his “deceivableness of unrighteousness...” (2 Thessalonians:2:8-10 [8] And then shall that Wicked be revealed, whom the Lord shall consume with the spirit of his mouth, and shall destroy with the brightness of his coming: [9] Even him, whose coming is after the working of Satan with all power and signs and lying wonders, [10] And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved.
See All... [3]). Clearly this applies to those left behind at the Rapture in a world ruled by Antichrist [2]; but it would seem that their rejection of the truth preceded and prepared them for “that man of sin” (v. 3,4) and thus could occur at least to a lesser degree before the Rapture.

The delusion causes “that they should believe a lie: That they all might be damned…” (v 11,12). Revelation:13:2And the beast which I saw was like unto a leopard, and his feet were as the feet of a bear, and his mouth as the mouth of a lion: and the dragon gave him his power, and his seat, and great authority.
See All... [4],4,8 says that the world will worship both “the beast” (Antichrist [2]) and “the dragon [Satan who] gave him his power, and his seat, and great authority.” Thus we could conclude that the lie is Antichrist [2]’s claim that he is God: “He as God sitteth in the temple of God, shewing himself that he is God” (2 Thessalonians:2:4Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
See All... [5]). The lie would seem to be the total delusion under Antichrist [2] and the false prophet which would include taking his mark and bowing down to his image. All who do so are damned (Revelation:14:9-11 [9] And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand, [10] The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb: [11] And the smoke of their torment ascendeth up for ever and ever: and they have no rest day nor night, who worship the beast and his image, and whosoever receiveth the mark of his name.
See All... [6]).