They’ve sent the same kinds of glossy mailers and hired the same types of media buyers, consultants and precinct walkers-for-hire.

But when it comes to California campaign-finance laws, the nearly two-dozen outside groups that have injected more than $9.3 million into the East Bay’s 7th Senate District special election are covered by much different rules. That makes it difficult for the public to keep track of the donations and spending behind it all.

Some outside groups active in the East Bay race had to file detailed compilations of donations and expenditures by a May 7 deadline. The public can download Excel files of that data from the Secretary of State’s website.

Other committees, though, did not have to file those reports. Voters can find information about their donations and spending – but only by going through hundreds of pages of electronic filings with the Secretary of State, which doesn’t have the capability to provide the data in Excel format.

Here’s the difference: So-called primarily formed committees, which support or oppose a specific candidate or ballot measure, have the same filing deadlines as the candidates in the Senate race – Assemblywoman Susan Bonilla and Orinda Mayor Steve Glazer, both Democrats. The committees had to file financial-disclosure reports May 7 covering the period from April 4 through May 2.

The most active committees covered by that rule all support Bonilla or oppose Glazer: Working Families Opposing Glazer for Senate 2015, Putting the East Bay First, and Million More Voters.

General-purpose committees, though, don’t have to file the same detailed compilations until July 31 – unless their spending in the Senate runoff exceeds 70 percent of their total for the previous two years. The most active outside spending groups covered by that rule all support Glazer or oppose Bonilla: the California Chamber of Commerce’s JobsPAC, EdVoice and California Charter Schools Association Advocates.

In the case of JobsPAC, its $977,000 in spending in the Senate runoff through Friday represents only about a quarter of the $4 million it reported spending during the 2013-14 election cycle.

Also, the Senate race features a third category of major outside spender: Southern California businessman Bill Bloomfield. Bloomfield, a “major donor” in the eyes of California campaign-finance regulators, had spent more than $2 million in the Senate race through Friday. He does not have to file a consolidated financial disclosure form.

The chart below shows outside spending, by week, in the contest. Hover over, or tap, for more information. Or click here. If using The Bees mobile app, click here.