It might have added a couple of points to the opponent's total, but Democrats wouldn't have won. They spent heavily in the slightly more Republican CA-39 and actually lost that district by 16 points. Some of McKeon's poor performance is due to McKeon himself. He spends his campaign money helping other Republicans, often sending buses of volunteers to places like Las Vegas, where he helped Joe Heck win NV-3. Ed Royce, in CA-39, spent heavily to defend his district.
The most Republican district they control in California was R+0.3 PVI. Even in a Presidential year this district should be a few points out of reach. Democrats have to hope the district becomes more Democratic before they have a shot at competing. Yet while some other districts move 3-4 points more Democratic, this district only went from R+3.4 to R+2.9. There's a shot that the district will be competitive in 2016 or 2020, but probably not in a mid-term and almost certainly not in 2014.
Rumors persist that McKeon is retiring. McKeon has denied those rumors. Yet they persist. My sources tell me that "only McKeon can answer that question." That's hardly the breakthrough scoop but it's certainly not a denial.
As I reported earlier, if McKeon retires Tony Strickland may run here. My sources tell me that Strickland would be the heavy favorite if he did so, that he actually represented some of the Santa Clarita Valley in the state senate and that he'd get the endorsement of both Congressman Kevin McCarthy and McKeon. Strickland is a prodigious fundraiser and that alone could scare off other Republicans.
Strickland's absence would open the door for Assemblyman Jeff Gorrell to run in CA-26. In 2012, Gorrell won an assembly district by 6 points that President Obama won by 7 points. He could run there again in 2014 and then run in the open SD-27 in 2016. President Obama got a two-party vote of 55.8% in SD-27 in 2012 and 55.2% in the similar CA-26. Gorrell may decide that while CA-26 is a difficult district to win, he'd rather try to do so in the more Republican leaning 2014 than 2016.