That's because Time/CNN seem to have stacked the deck by significantly overestimating the number of Democrats likely to vote in this year's strong anti-Obama electorate.
According to the Weekly Standard's Jay Cost, the Time/CNN poll seems to think that Democrats will have more of their voters this year than in their banner 2008 year. Cost examined the Time/CNN numbers, compared them to exit polls from previous elections, and concluded - accurately, I believe - that the poll significantly oversampled Democrats.
Virtually every measure that can be used to predict election results at this stage - party ID, party favorability ratings, generic ballot, voter enthusiasm, political ideology - all point to a Rpublican Party that is in a better position now than it was two years ago.
Furthermore, Democrats do not have a popular presidential candidate to encourage voter turnout or a deeply disliked presidential incumbent against whom they can rally supporters.
And yet, as Cost reported today:
Yesterday evening, the CNN/Time poll of the California Senate race found Barbara Boxer up nine points among likely voters over Carly Fiorina.
That's by about the same amount that John Kerry beat George W. Bush in 2004. Yet Kerry defeated Bush among independent voters by a wide margin, 59-36. In the CNN/Time poll, it's Fiorina who has a lead over Boxer among independents, and a sizeable one at that, 53-39. The poll also finds the two parties very well sorted, Democrats going for Boxer 93-5 and Republicans going for Fiorina 92-4.
So, the only way to find a nine-point lead for Boxer is if the poll has a huge sample of Democrats.
To illustrate his point, Cost takes the proportions of Democrats and Republicans that favor each candidate according to the CNN/Time poll, and matches them up with turnout numbers from the past three election cycles. The results show that Democratic turnout would have to be larger this year than it was in 2008. That is simply not going to happen.
So the only way the poll could have reached that conclusion is if it over-sampled Democrats.
Cost runs the same analysis on the poll's findings in the Governor's race - which showed state Attorney General Jerry Brown leading Meg Whitman by a nine-point margin, despite the latter's sizable majority among independents. The results were virtually the same.
Cost created these two charts to illustrate his analysis:
"If the partisan mix is recalculated to reflect the spreads in 2006 or 2004," Cost notes, "then we have a dead heat in California."
"I appreciate the need for leeway in partisan sampling, but it seems quite unlikely that the 2010 midterm electorate will look like this."
Other polls show much closer races in both contests. In the governor's race, Rasmussen shows Brown up one point, Field claims the race is dead even, and a Public Policy Institute of California poll even shows Whitman leading by a point.
Polls of the Senate race are not quite so kind to the GOP contender, but still show a much tighter race than the CNN/Time poll. Rasmussen shows a deficit of 4 for FIorina, Field has Boxer up by 6, and PPIC by 7.