Marginal modal dare means to have the courage to do something. It's marginal because it's privy to both auxiliary verb and main verb classes.
Main verbs inflect for number and carry tense; dare does that; e.g., she dares; He dared me. Main verbs subcategories for (i.e., take) objects; e.g., I dare you; Dare to sleep. Moreover, main verbs have helping verbs. DO-insertion is an example of a helping verb; e.g., He doesn't dare; emphatic, I do dare! The verb DO (do, does, did) is an auxiliary verb. If you see it and dare together, you know that dare is functioning as a main verb. Here's an example of that:
1 Does he dare to come here? <main verb>
Now, given that 'marginal' dare is privy to both auxiliary and main verb classes, it can do both jobs on its own. That is, it doesn't need a helping hand, sort to speak. DO isn't needed. Example A, below, is an example of that. Subject-verb inversion, better known as question formation, results in:
A Dare he come here? <auxiliary>
In A, auxiliary dare and the subject he switched places. The same process occurs here:
2 Did you dare to contradict her? <main verb>
B Dared you contradict her? <auxiliary verb>
In B, dared carries the past tense marker -d. Auxiliaries do that; e.g., Do I? Did I? Auxiliaries also occur before (precede) the negative adverb not, as in these final examples:
3 He does not dare to show himself in front of us. <auxiliary>
C He dare not show himself in front of us. <auxiliary>
4 I did not dare to answer back. <auxiliary>
D I dared not answer back. <auxiliary>
As for semantics,
"Modal need and dare convey modal overtones, viz. volitional force, advice or warning. Contrast needn't (and obsolescent daren't) with doesn't need to and doesn't dare to, and note the advisory vs. neutral thrust of the respective variants. Contrast negated modal needn't with doesn't before non-modal need. Another syntactic difference is that the modal takes a short infinitive (i.e. without to).
C J Bailey: Grammar Series I, l992, Appendix cited in Latin. Why Study it at all?
With regard to modal need,
...dare is "very much like auxiliary need": both are modals occurring only in non-affirmative contexts and taking a bare infinitival complement. But there are some differences between dare and need, which we decided we didn't have room to mention. Here are the two main ones:
- Auxiliary dare, unlike auxiliary need, has a preterite form: we see it in I dared not tell anyone. The placement of not after the verb here shows this is auxiliary dare. Notice, however, that there is no negative preterite form *daredn't.
- Lexical dare, unlike lexical need, is found with a bare infinitival complement as well as the to-infinitival. In the following examples, illustrates the bare infinitival construction, [ii] the to-infinitival:
ia. I wouldn't dare jump out.
b. *I wouldn't need ask for help. [ungrammatical]
iia. I wouldn't dare to jump out.
b. I wouldn't need to ask for help.
SourceHope that helps.
Chapter 3, page 41: more on the strange modal verb dare