and that our Gospel came to you not in word only, but also in power, and in the Holy Spirit, and with much assurance. You know what kind of men we showed ourselves to be among you for your sake.
Our gospel ...  Paul on occasion could say "my" gospel; and therefore the thought persists that the construction here is for the purpose of affirming the oneness of the gospel the Thessalonians had received with the same gospel taught by all of the apostles.  Note that the acceptance of that gospel by the Thessalonians was one of the reasons that Paul spoke so confidently of their being the election of God. Those who accept the gospel in all generations are likewise of the elect.