Counting nouns using "slew" and the grammatical implications

Question

Just having a lively debate with a content writer over whether we should say

There are a slew of reasons...

or

There is a slew of reasons...

Read this article which suggests that different words are treated differently in this situation, so I'm wondering if slew would behave more like number, as in, There are a number of reasons, or if it would be more like group, as in There is a group of people that believe....

Any thoughts on how one can decide for a word like slew?

Possible duplicate of: a number of vendors is/are? Is the sentence "There is a large number of labourers who want to migrate to Japan for work." correct?

Answer 1

slew is defined at ODO as

A large number or quantity of something.

M-W

a large number

dictionary.com

a large number or quantity

So it's a number, not a group, and therefore gets the plural verb "there are".