Source of graph: online version of the WSJ article quoted and cited below.
(p. A1) PHILADELPHIA–U.S. labor unions are plowing money into the 2016 elections at an unprecedented rate, largely in an effort to help elect Hillary Clinton and give Democrats a majority in the Senate.
According to the most recent campaign-finance filings, unions spent about $108 million on the elections from January 2015 through the end of August [2016], a 38% jump from $78 million during the same period leading up to the 2012 election, and nearly double their 2008 total in the same period. Nearly 85% of their spending this year has supported Democrats.
For the full story, see:
BRODY MULLINS, REBECCA BALLHAUS and MICHELLE HACKMAN. “Labor Unions Step Up Presidential-Election Spending.” The Wall Street Journal (Weds., Oct. 19, 2016): A1 & A4.
(Note: ellipsis, and bracketed year, added.)
(Note: the online version of the story has the date Oct. 18, 2016, and has the title “Unions Up the Election Ante.”)