Some calculations based on the 2008 polls published thus far (from RCP) are below the fold.

Crossposted at Daily Kos.

A) Polls that asked both the "with Gore" and "without Gore" questions:

1.

FNOD, 5/15-16

With Gore:

Clinton: 35%
Obama: 20
Gore: 13
Edwards: 13
Richardson: 4

Clinton-Obama Margin: 15

Without Gore (with shifts in parentheses):

Clinton: 39% (+4)
Obama: 23 (+3)
Edwards: 15 (+2)
Richardson: 4 (0)

Clinton-Obama Margin: 16

Interesting "without Clinton" results:
Obama: 34 (+14)
Gore: 23 (+10)
Edwards: 16 (+3)
Richardson: 5 (+1)
(which shows that Obama and Gore have the best capacity to pull support from Hillary)

2.

Cook/RT, 5/11-13:

With Gore:

Clinton: 35%
Obama: 24
Gore: 10
Edwards: 11
Richardson: 2

Clinton-Obama Margin: 11

Without Gore (with shifts in parentheses):

Clinton: 40% (+5)
Obama: 25 (+1)
Edwards: 13 (+2)
Richardson: 2 (0)

Clinton-Obama Margin: 15

3.

CNN/OR 5/4-6
With Gore:

Clinton: 38%
Obama: 24
Gore: 12
Edwards: 12
Richardson: 5

Clinton-Obama Margin: 14

Without Gore (with shifts in parentheses):

Clinton: 41% (+3)
Obama: 27 (+3)
Edwards: 14 (+2)
Richardson: 6 (+1)

Clinton-Obama Margin: 14

4.

USA Today

With Gore:

Clinton: 38%
Obama: 23
Gore: 14
Edwards: 12
Richardson: 2

Clinton-Obama Margin: 15

Without Gore (with shifts in parentheses):

Clinton: 45% (+7)
Obama: 27 (+4)
Edwards: 14 (+2)
Richardson: 3 (+1)

Clinton-Obama Margin: 18

Averages:

With Gore:

Clinton: 36.5%
Obama: 22.75
Gore: 12.25
Edwards: 12
Richardson: 3.25

Clinton-Obama Margin: 13.75
Also, Obama+Gore = 35%

Without Gore (with shifts in parentheses):

Clinton: 41.25% (+4.75)
Obama: 25.5 (+2.75)
Edwards: 14 (+2)
Richardson: 3.75 (+0.5)

Clinton-Obama Margin: 15.75

B. Polls that asked or reported only the "without Gore" question:

1.

ARG, 5/9-12

Clinton: 39%
Obama: 22
Edwards: 19
Richardson: 2

Clinton-Obama Margin: 17

2.

Rasmussen, 5/07-10

Clinton: 35%
Obama: 33
Edwards: 14
Richardson: 3

Clinton-Obama Margin: 2

Average:

Clinton: 37%
Obama: 27.5
Edwards: 16.5
Richardson: 2.5

Clinton-Obama Margin: 9.5

C. Poll that asked or reported only "with Gore" question:

Gallup, 5/10-13

With Gore:

Clinton: 35%
Obama: 26
Gore: 16
Edwards: 12
Richardson: 2

Clinton-Obama Margin: 9

One notes that Obama's and Gore's number in this last poll add up to 42, 7 points more than Clinton.