But the two term Democratic Congressman claimed victory Wednesday night in the 11th district over his Republican rival David Harmer.
McNerney's lead was at 1,681 votes, a lead his campaign called "insurmountable," according to Politico.com.
The Democrat's seat was seen as vulnerable by many after McNerney narrowly defeated longtime Republican Congressman Richard Pombo in 2006. The 11th district is made up of diverse constituents in parts of Alameda, Contra Costa, San Joaquin and Santa Clara counties.
In 2008, McNerney held off Republican challenger Dean Andal by six percentage points. With the tide of anti-Democrat sentiment sweeping across the nation, some Republican pundits had picked McNerney's seat as one up for grabs in California.
But there are still about 11,000 votes that need to be counted in the race. McNerney's campaign is claiming victory relying on current voting trends to carry out through the remaining ballots.