In Reasonable Faith, Philosophical Foundations for a Christian Worldview, and in several places online (here, for example), William Lane Craig endorses a modified version of Plantinga's Reformed Epistemology. According to Craig's version, the Christian can know that Christianity is true in the basic (i.e.,immediate, non-inferential) way by means of "the self-authenticating witness of the Holy Spirit". As Craig summarizes his view:
. . . the experience of the Holy Spirit is veridical and unmistakable (though not necessarily irresistible or indubitable) for him who has it; that such a person does not need supplementary arguments or evidence in order to know and to know with confidence that he is in fact experiencing the Spirit of God; that such experience does not function in this case as a premiss in any argument from religious experience to God, but rather is the immediate experiencing of God himself; that in certain contexts the experience of the Holy Spirit will imply the apprehension of certain truths of the Christian religion, such as "God exists," "I am condemned by God," "I am reconciled to God," "Christ lives in me," and so forth; that such an experience provides one not only with a subjective assurance of Christianity's truth, but with objective knowledge of that truth; and that arguments and evidence incompatible with that truth are overwhelmed by the experience of the Holy Spirit for him who attends fully to it.
Although both Plantinga's and Craig's models of warrant-basic belief in Christian theism make essential reference to the activity of the Holy Spirit, Craig's model differs from Plantinga's in terms of the means by which the Holy Spirit's activity generates such belief:
Plantinga's model involves crucially what is usually called the inner witness of the Holy Spirit. In his model the Holy Spirit functions on the analogy of a cognitive faculty, producing beliefs in us. I myself prefer to think of the Spirit's witness either as a form of literal testimony or else as part of the experiential circumstances which serve to ground belief in God and the great truths of the Gospel. In either case His deliverances are properly basic.(ibid)
Furthermore, Craig is a bit more explicit than Plantinga with respect to whether he thinks such Holy-Spirit-generated belief can function as an intrinsic defeater-defeater for objections to Christianity:
Plantinga does not to my knowledge clearly commit himself to the view that the witness of the Holy Spirit is an intrinsic defeater-defeater. Such a thesis is independent of the model as presented. But I have argued that the witness of the Spirit is, indeed, an intrinsic defeater of any defeaters brought against it. For it seems to me inconceivable that God would allow any believer to be in a position where he would be rationally obliged to commit apostasy and renounce Christ. It seems to me rather that in such a situation a loving God would intensify the Spirit's witness in such a way that it becomes an intrinsic defeater of the defeaters such a person faces. (Ibid. Emphasis mine.)
Two common complaints about William Lane Craig's "Holy Spirit epistemology" (to borrow an expression from Michael Martin) are that (i) it's a form of fideism and that (ii) it's an unacceptable form of dogmatism. According to (i), Craig is asserting that one can know that Christianity is true without evidence (or at least without sufficient evidence). According to (ii), Craig inappropriately asserts that one can and should believe that Christianity is true even if no arguments for God are persuasive, and even if there is very strong evidence against Christianity. I think that both criticisms of Craig's Holy Spirit epistemology fail. However, I think there is a successful criticism of it that grants the failure of (i) and (ii).
First, though, here is why I think criticisms (i) and (ii) fail. The basic problem is that both fail to appreciate the core idea of Craig's Holy Spirit epistemology: Craig takes the internal testimony of the Holy Spirit to present the truth of the Christian faith in such a way that it's on a par with ordinary Moorean facts (or at least beliefs roughly analogous to such in terms of force, vivacity, and warrant. Hereafter I leave this qualification implicit). That is, (following Plantinga) Craig thinks the internal testimony of the Holy Spirit presents the truth of the Christian faith in such a way that it's on a par with the claims that I exist, that material objects exist, and that there are other minds besides my own. This comes out in the analogies he mentions in his discussions of his account. Thus, he appeals to Plantinga's "purloined letter case" to illustrate the notion of an intrinsic defeater-defeater, which can be summarized as follows:
The Purloined Letter Case: Suppose I have means, motive, and opportunity to steal an embarrassing letter that was in fact stolen from the office of my department chair. There is also very strong evidence against me (e.g., I've been known to steal in the past; a trustworthy colleague says he saw someone who looks like me enter the Dean's Office on the day of the incident, etc.). However, I have a clear and vivid memory of being alone in the woods all day on the day of the incident. In this case, I'm rational to retain my belief that I didn't steal the letter because of my memory, even without propositional evidence and argument that could defeat the reasons brought against me. My memory of being alone in the woods all day on the day of the incident is thus an intrinsic defeater-defeater of the claim that I stole the letter.
The "I'm Alive" Case: "Pick any belief that you hold confidently and then imagine a state of affairs in which that belief would be false if that state of affairs obtained. For example, I am absolutely sure that I am alive; but if someone were to discover a grave containing my bones, then that belief would be falsified. Should I worry?"
In both cases, it's not prima facie implausible that the corresponding beliefs (that I was alone in the woods all day; that I'm alive, etc.) are justified or warranted in the basic (i.e., direct, non-inferential) way. Furthermore, it's not prima facie implausible to think that in such cases, the force, vivacity, and warrant such beliefs enjoy is so strong that they can function as intrinsic defeaters of very strong evidence against them. And Craig (following Plantinga) is arguing that Christian belief, when grounded in attentiveness to the internal testimony of the Holy Spirit, is sufficiently relevantly similar to such cases in terms of force, vivacity, and warrant. Therefore, since the latter can function as intrinsic defeaters to virtually any evidence that comes into conflict with them, so, likewise, can the former.
Given this sketch of Craig's variation on Plantinga's Reformed Epistemology, we can see why criticisms (i) and (ii) fall far short of being persuasive. First, criticism (i) is less than persuasive, since most will not find the acceptance of ordinary Moorean facts to be a form of fideism. So if the internal testimony of the Holy Spirit presents the truth of Christianity in such a way that it's on a par with ordinary Moorean facts, then such people should likewise grant that acceptance of the former is not a form of fideism.
Criticism (ii) is less than persuasive as well. For it's not obviously inappropriate to accept Moorean facts even in the face of seemingly good arguments and evidence to the contrary (cf. The Purloined Letter Case and the "I'm Alive" Case). So if the internal testimony of the Holy Spirit presents the truth of Christianity in such a way that it's on a par with ordinary Moorean facts, then it might well be appropriate for such people to likewise accept the former in the face of seemingly good arguments to the contrary. (At least I grant this for the sake of argument.)
Although I find criticisms (i) and (ii) less than persuasive, I think there is a simple yet decisive criticism of Craig's Holy Spirit epitemology: at least for the majority of Christians, the Holy Spirit (if such there be) fails to present the truth of Christianity in such a way that it's anywhere near being on a par with ordinary Moorean facts. In this regard, Craig's Holy Spirit epistemology suffers from a key problem shared by Plantinga's account of warranted Christian belief. Therefore, as with Plantinga's account, Craig's account fails to provide an epistemically possible account of how Christian belief can be warrant-basic for the typical Christian (or at least how Christian belief can enjoy sufficient warrant to function as an intrinsic defeater-defeater for strong objections to it).