what does “mark” mean here?
Former President Barack Obama officially endorsed his former vice president, Joe Biden, on Tuesday, marking the Democratic establishment's formal consolidation around the party's presumptive presidential nominee.

Hi, what does “mark” mean here?
Does it mean celebrate?
I tried to find the meaning on dictionaries but I still have no idea.

Question

what does “mark” mean here?
Former President Barack Obama officially endorsed his former vice president, Joe Biden, on Tuesday, marking the Democratic establishment's formal consolidation around the party's presumptive presidential nominee.

Hi, what does “mark” mean here?
Does it mean celebrate? 
I tried to find the meaning on dictionaries but I still have no idea.

Answer

Thanks everyone

Answer

"Mark" in this case, is equivalent to "establish" or "verify".

Answer

Who or what is the agent  of the verb "mark" here?
I think it as the sentence before the word "marking":
Former President Barack Obama officially endorsed his former vice president, Joe Biden, on Tuesday.
such sentence is the agent of the verb "mark" here.

Answer

Creating and recording a significant event.

Answer

"Mark" means that it is a significant event. More commonly, to mark is to make an imprint on something or to label something. A "mark" in history is a moment that is significant for some historical reason.