3 added 60 characters in body
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Jelly, 15 15  14 bytes

ḲJɓḲ⁾""j$€⁹¦Kð€Ḳ⁾""j$€⁹¦K¥ⱮJ$

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How?

ḲJɓḲ⁾""j$€⁹¦Kð€Ḳ⁾""j$€⁹¦K¥ⱮJ$ - Link: list of characters, S
Ḳ               - split (S) at spaces -> A
 J             $ - rangelast oftwo lengthlinks as a monad:
           -> I = [1,2,map...len(A)]
  ɓ          ð€ -J for each- (i in I)...across: withrange swappedof argumentslength -> [f(S,I 1),= f(S[1,2), ...len(A)]
           ¥    -   split...doing: (S)last attwo spaceslinks ->as B
a dyad: i.e. f(A, i) for i in I
      € ¦      -     sparse application...
              -     ...to indices: chain's right argument, i
      $  $       -     ...action: last two links as a monad:
  ⁾""  ⁾""         -       literal list of characters = ['"', '"']
     j  j        -       join (with B[i]A[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
          K  K   -     join with spaces

Jelly, 15 bytes

ḲJɓḲ⁾""j$€⁹¦Kð€

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How?

ḲJɓḲ⁾""j$€⁹¦Kð€ - Link: list of characters, S
Ḳ               - split (S) at spaces -> A
 J              - range of length -> I = [1,2,...len(A)]
  ɓ          ð€ - for each (i in I) with swapped arguments -> [f(S, 1), f(S,2), ...]
               -   split (S) at spaces -> B
         € ¦    -   sparse application...
              -   ...to indices: chain's right argument, i
        $       -   ...action: last two links as a monad:
    ⁾""         -     literal list of characters = ['"', '"']
       j        -     join (with B[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
            K   -   join with spaces

Jelly,  15  14 bytes

Ḳ⁾""j$€⁹¦K¥ⱮJ$

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How?

Ḳ⁾""j$€⁹¦K¥ⱮJ$ - Link: list of characters, S
Ḳ              - split (S) at spaces -> A
             $ - last two links as a monad:
           -   map...
            J  -   ...across: range of length -> I = [1,2,...len(A)]
          ¥    -   ...doing: last two links as a dyad: i.e. f(A, i) for i in I
      € ¦      -     sparse application...
              -     ...to indices: chain's right argument, i
     $         -     ...action: last two links as a monad:
 ⁾""           -       literal list of characters = ['"', '"']
    j          -       join (with A[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
         K     -     join with spaces
2 deleted 52 characters in body
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Jelly, 1615 bytes

ḲJɓḲ⁾""j$€⁹¦Kð€YḲJɓḲ⁾""j$€⁹¦Kð€

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How?

ḲJɓḲ⁾""j$€⁹¦Kð€YḲJɓḲ⁾""j$€⁹¦Kð€ - Link: list of characters, S
Ḳ                - split (S) at spaces -> A
 J               - range of length -> I = [1,2,...len(A)]
  ɓ          ð€  - for each (i in I) with swapped arguments -> [f(S, 1), f(S,2), ...]
   Ḳ             -   split (S) at spaces -> B
         € ¦     -   sparse application...
          ⁹      -   ...to indices: chain's right argument, i
        $        -   ...action: last two links as a monad:
    ⁾""          -     literal list of characters = ['"', '"']
       j         -     join (with B[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
            K    -   join with spaces
               Y - join with newlines

Jelly, 16 bytes

ḲJɓḲ⁾""j$€⁹¦Kð€Y

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How?

ḲJɓḲ⁾""j$€⁹¦Kð€Y - Link: list of characters, S
Ḳ                - split (S) at spaces -> A
 J               - range of length -> I = [1,2,...len(A)]
  ɓ          ð€  - for each (i in I) with swapped arguments -> [f(S, 1), f(S,2), ...]
   Ḳ             -   split (S) at spaces -> B
         € ¦     -   sparse application...
          ⁹      -   ...to indices: chain's right argument, i
        $        -   ...action: last two links as a monad:
    ⁾""          -     literal list of characters = ['"', '"']
       j         -     join (with B[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
            K    -   join with spaces
               Y - join with newlines

Jelly, 15 bytes

ḲJɓḲ⁾""j$€⁹¦Kð€

Try it online!

How?

ḲJɓḲ⁾""j$€⁹¦Kð€ - Link: list of characters, S
Ḳ               - split (S) at spaces -> A
 J              - range of length -> I = [1,2,...len(A)]
  ɓ          ð€ - for each (i in I) with swapped arguments -> [f(S, 1), f(S,2), ...]
   Ḳ            -   split (S) at spaces -> B
         € ¦    -   sparse application...
          ⁹     -   ...to indices: chain's right argument, i
        $       -   ...action: last two links as a monad:
    ⁾""         -     literal list of characters = ['"', '"']
       j        -     join (with B[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
            K   -   join with spaces
1
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Jelly, 16 bytes

ḲJɓḲ⁾""j$€⁹¦Kð€Y

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How?

ḲJɓḲ⁾""j$€⁹¦Kð€Y - Link: list of characters, S
Ḳ                - split (S) at spaces -> A
 J               - range of length -> I = [1,2,...len(A)]
  ɓ          ð€  - for each (i in I) with swapped arguments -> [f(S, 1), f(S,2), ...]
   Ḳ             -   split (S) at spaces -> B
         € ¦     -   sparse application...
          ⁹      -   ...to indices: chain's right argument, i
        $        -   ...action: last two links as a monad:
    ⁾""          -     literal list of characters = ['"', '"']
       j         -     join (with B[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
            K    -   join with spaces
               Y - join with newlines