Of the 10 special-interest sectors giving the most money to state legislators over the past two years, labor unions accounted for four of the spots and nearly half of money given by those elite donors, according to an analysis by MapLight.org. The group studies campaign contributions and their correlations to votes cast by elected officials.

Combined giving by the top 10 in 2011 and 2012 was $23.7 million, with labor giving $11.4 million and public labor unions alone accounting for $7 million. Here’s the list:

1. Construction unions – $4,362,843

2. Attorneys, law firms – $2,995,623

3. Native American tribes, governing units – $2,902,050

4. State, local government employee unions – $2,701,515

5. Police, firefighter unions – $2,679,467

6. Property, casualty insurance – $2,023,238

7. Telecommunications – $1,986,976

8. Teachers unions – $1,624,125

9. Pharmaceutical manufacturing – $1,219,851

10. Real estate – $1,182,545

Union watchers, particularly in Orange County, are well aware of the financial muscle of labor. Last year’s Measure V in Costa Mesa called for, among other things, a ban on automatic union employee payroll deductions for political purposes. It was defeated by a 3-2 margin after unions outspent proponents by 10-1.

But union money isn’t always blamed by critics. Last year’s Proposition 32, which would have instituted a statewide ban on those payroll deductions, saw unions and their allies spend about $75 million to defeat the measure. Proponents didn’t quite have that much, but thanks to out-of-state assistance raised about $60 million.

That out-of-state assistance eventually resulted in a $1 million civil settlement paid by a pro-Prop. 32 PAC, because donors were wrongly kept anonymous. But a settlement was announced last month and the mystery donors probably had minimal negative blowback on the poll results. Prop. 32 author Mark Bucher told me after the election that they had enough money to run their campaign and that they’d probably try again with a better campaign strategy.

Mimi’s money

MapLight, founded in 2005 with a focus on congressional votes and contributions, launched its California webpage in August. The site shows correlations between campaign contributions and votes cast on bills in Sacramento going back to 2009, and has a tool that allows you to search the secretary of state’s campaign finance pages in new ways. It also has a bunch of cool related charts, like the 10 biggest fundraisers in the Assembly and in the Senate.

The sole Orange County legislator to make the list is Sen. Mimi Walters, R-Irvine. She came in eighth in the Senate, raising $2.2 million from 2009 through 2012. She’s now running to replace retiring U.S. Rep. John Campbell, R-Irvine. She can’t transfer money from her state account to her congressional campaign – but the Senate dough is nonetheless a testament to her fundraising prowess, particularly since she ran as an incumbent without a significant challenger in her sole election during that period.

The Legislature’s top fundraisers? In the Senate, Cathleen Galgiani, D-Stockton, with $3,350,480. In the Assembly, Ken Cooley, D-Rancho Cordova, with $4,113,825.

Contact the writer: 714-796-6753 or mwisckol@ocregister.com