Why does the editor write a
"comma" before in which?
Since there is a "comma", I think that the which is refer to headline not Politico.
ATTENTION: NOT A TEACHER
(1) You have asked a great question. I do
not claim to have
the answer, but I wish
to share some thoughts:
(a) Kindly remember that commas are not "grammar." Over the years, native speakers
have decided to punctuate sentences a certain way. One "rule" is:
Do not set off restrictive clauses with a comma (clauses that are vital to the
meaning of a sentence); use commas to set off non-restrictive clauses (those
with interesting -- but not vital -- information).
(2) I most respectfully suggest that the adjective clause in your sentence is
non-restrictive (grammatically speaking). The main idea is simply:
This really is the headline of Jonathan Martin's
Politico piece
.
(a) IMHO, the words "in which he investigates ...." are strictly non-restrictive.
They have been added to assist people who may not have heard about Mr. Martin's
piece in
Politico.
(3) Now look at this sentence that I have made up: I want you to read Jonathan
Martin's
Politico piece in which he investigates ....
(a) You notice that there is no comma. Why? Because the adjective clause contains
vital information for identification. Presumably, Mr. Martin has written more than one piece for
Politico:
Teacher: I want you to read Jonathan Martin's
Politico piece.
Student: Excuse me, sir.
Which piece by Mr. Martin? He has written ten.
Teacher: Oh, excuse me. I'm referring to the piece in which he investigates ....
Student: Thank you, sir, for identifying which piece.
(4) I agree with Teacher Bennevis that this
non-restrictive clause modifies the word
"piece." (That is, the article in the newspaper and website called
Politico.).
(5) Furthermore, as Teacher Bennevis told us, sometimes (often?) we have to forget
"rules" and use commion sense. How can the rumors about that gentleman be
investigated in a headline?
UPDATE:
I have just noticed that Teacher Bob has pointed out that the word "headline" in that
sentence really means the "gist." That is,
the main point (of the article).
In other words, that article said certain things. The article's main point will be the
the headline in many newspapers that decide to report what was said in the article.