The Republicans are working on getting a Proposition on the June 2008 that would award one electoral vote to the winner of each of California's 53 Congressional district, and 2 for the statewide winner. How would this effect California's competitiveness in Presidential elections?
Kerry won California by 9.95 points.
Kerry won 31 Congressional districts by an average of 33.88 points.
Bush won 22 Congressional districts by an average of 18.67 points.
The average Congressional district was won by 27.56 points.
As we can see, the average Congressional district is much less competitive than the state as a whole. A swing of 10 points to the Republicans would give the Republicans only 2 more Congressional districts, while it'd swing the winner of California. Of course, if the Democrat wasn't going to win California, they've already lost the election.
Bush would have gotten 22 electoral votes in 2004. 19 of these Congressional districts voted Republican by at least 11.3 points. Republicans can completely screw over California, and still get those 19 electoral votes.
From this site
Democratic margin of victory by district in California
09 73.3
08 70.5
33 66.9
35 59.0
31 55.4
37 48.4
12 44.4
28 43.1
13 43.0
06 42.2
34 39.0
14 38.2
07 35.3
30 33.4
17 32.6
38 31.7
16 27.9
15 27.0
32 25.7
29 23.9
53 23.5
05 23.2
01 21.4
27 20.1
36 19.4
39 18.3
10 18.1
23 18.0
43 17.5
51 7.6
20 2.2
18 -0.2
47 -1.4
11 -8.7
50 -11.3
26 -11.5
24 -12.7
45 -13.0
46 -15.3
03 -17.4
48 -18.0
25 -18.9
34 -19.1
40 -21.8
19 -23.3
52 -23.7
04 -23.9
41 -24.9
42 -25.2
02 -25.5
49 -26.1
21 -31.8
22 -37.0
Note that 11,18, and 47 voted for Bush, but have Democratic representatives.