くださるんじゃ…: Formal, semi-casual, poor usage, etc.?

Question

それって先生が決めて、一緒に行ってくださるんじゃ…。

*From Japanesetest4you.

My understanding:

1. くださる is the honorific version of くれる

2. ん is from の, explanatory

3. じゃ, contracted では, usually in the form of rhetorical じゃない, or the slangy じゃん

My problem here:

1. Is ない left out of the sentence? I think I've only seen じゃない/じゃん so far.

2. くださる is 尊敬語 unless I had been hopelessly mistaken for months. However, this くださるんじゃ somehow looks, and sounds really casual to me. Is the speaker sneaking in a hint of 砕けた言い方 in the guise of 敬語? I also feel that by speaking this way, the speaker is hiding a sense of affected ignorance of responsibility, but I may be reading too much into this.

教えていただけませんか。お願いいたします！

Answer 1

1. 「ないんですか？」 or something similar is left out after 「～んじゃ...」

The full sentence would be like:

それって先生が決めて、一緒に行ってくださるんじゃないんですか？

but it's quite common to cut off sentences like this in daily conversation. And I think you'd usually sound a bit less decisive/interrogatory and therefore a bit more humble and softer when speaking this way.

Example:

「これって、間違ってるんじゃないですか？」→「これって、間違ってるんじゃ・・・」

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2. You're right that 「くださるんじゃ…」 is a bit more casual than 「くださるのでは…」. 「くださるのでは（ないのですか？ / ありませんか？）」 would sound more formal.