The California Majority Report, a left-wing blog run by Steve Maviglio, Deputy Chief of Staff and Communications Director to Assembly Speaker Fabian Nunez, is blogging the Doolittle will announce tomorrow that he is not seeking re-election and that Rico Oller will get in:

This Time It's For Real: Doolittle to Drop Out, Oller in for Congressional Seat

Embattled Congressman John Doolittle, the focus of a federal corruption probe, will announce that he will not seek re-election paving the way for former State Sen. Rico Oller for the 4th District Congressional seat, the California Majority Report has learned. The move, first noted back in November in the Stockton Record, could come as early as this week.
 
Oller served in the Assembly and for one-term in the Senate before narrowly losing a brutal GOP primary for the neighboring Third Congressional seat in 2004 against now-Congressman Dan Lungren and Mary Ose, sister of former Congressman Doug Ose. Oller is a slick ultra-right conservative cut from the same cloth as Doolittle. In his last race for Congress, Oller enjoyed strong support from religious conservatives, anti-tax zealots, and the NRA. Oller has considerable personal wealth to fund his campaign, and owns property in the 4th District.
 
But Oller's toughest GOP challenger may be Assemblymember/Insurance Agent Ted Gaines of Roseville, who was a two-term member of the Placer County Board of Supervisors before being elected to the legislature in 2006. Gaines has been an ineffective legislator, but, like Oller, has conservative credentials. His goal in the legislature, according to his website: "I look forward to working to make sure our state is not overrun by the liberals from San Francisco and Los Angeles."

You can read the whole post yourself here.  You can decide for yourself if the information is reliable.  Steve Maviglio is a liberal Democrat, but he has great contacts.

[Edit, 9:29 AM, - Maviglio is not reporting that this announcement is tomorrow.  I have that from my own source.  Maviglio is just reporting that the decision has been made.]