As / Like with "should"? "acts like a president should" vs. "acts as"

Clearly the first is wrong - because like can go with nouns or pronouns, never a clause.
But the second one is also suspect IMO, ellipsis usage is not completely correct while usage of "as" is correct.

He acted as a president should have --> Correct. (acted is implied after "acted" and the complete sentence reads "He acted as a president should have acted"). The complete verb need not be repeated here because "acted" can very well sit with the present perfect construction and the helping verb is good enough to capture the idea.

He acted as a president should act --> Correct. (Presidents should act in a certain way (a general fact) and he acted accordingly (a past tense verb)). The complete verb must be repeated after "as" because the tense has changed.

He acted as a president should -> Incorrect IMO, because the verb that ellipsis is trying omit should be seen verbatim in other parts of the sentence.
"He acted as a president should (acted)" doesn't make sense.

Thank you for some really great answers, everyone! Kudos to all of you!

On a general note - can you guys tell me if there's a consolidated resource somewhere on gmatclub or externally that I can use to get my head around the more advanced SC stuff? I'm already looking at the "downloads" and some good question compilations + Ron's videos. MGMAT forum is also helpful, but I find there are many nuances that I should be familiar with, which I am not.

Ideally, I'm looking for something that will explain an advanced concept, and then give some problems on it right away for practice.

Hi...I was in the same situation as you are in now. I had finished my SC preparation from e-gmat and I was confident enough that I would score 80% accuracy in verbal SC. To my shock, I scored 33% accuracy, then I came across these 2 attachments in GMAT club and I analysed each and every option of each question again and again for 4 days very slowly and then I understood few concepts very well. I would suggest that you do the same and find the difference. Now I am confident that I would not go wrong in 600 level questions and many 700 level questions. For the questions in the comparisons attachment, I suggest that you check for the Expert replies in GMATclub.

All the best. Feel free to PM me for any other info

P.S. This is the basic step to be taken to feel confident enough about many topics in SC. You have to follow some additional steps once you reach 700 level. However, I believe that you have to solidify your concepts at the moment.


Please give a kudos, if you feel this post is helpful.

my bookmarks related to comparisons. might be helpful.
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https://gmatclub.com/forum/how-far-ellip ... 48973.html
https://gmatclub.com/forum/ellipsis-subs ... 46823.html
https://magoosh.com/gmat/2013/auxiliary- ... -the-gmat/
https://magoosh.com/gmat/2013/repeating- ... -the-gmat/
https://magoosh.com/gmat/2013/dropping- ... -the-gmat/
https://gmatclub.com/forum/sentence-corr ... 93452.html
https://gmatclub.com/forum/the-guiding-p ... 51-80.html

you might want to keep some simple facts / rules related to like & as
1. like is always a preposition - just nouns or pronouns can follow like.
2. "as" when used for comparisons, is always a conjunction - so it must be followed by a clause. ( or in some situations a prepositional phrase - where the clause is implied)

Pls note "as" has other functions besides it's usage in comparisons
- Causality : I post to Gmatclub forums regularily, As it has a highly active user-base. (As = reason why / because )
- Timing of actions : I noticed a very interesting article on SC, as I was browsing through the forums (as = while )
- Role assignment : example - As a GMAT Test Taker , I visit Gmatclub regularily. (As = I am playing the role of Gmat test taker)

you may have noticed that comparisons use "as" as a conjunction
(! phew, the unquoted as in previous sentence denotes the role of as - used as a preposition )