* Money will go to Super Pac, another organization
* Soros had largely remained on sidelines
By Alina Selyukh
WASHINGTON, May 7 (Reuters) - George Soros is pledging $2 million to two outside groups supporting progressive causes and helping President Barack Obama's re-election campaign and other Democrats running in November, a Soros advisor said on Monday.
Soros adviser Michael Vachon said in an email that the billionaire investor is concentrating his giving on grassroots organizing and "holding conservatives accountable for the flawed policies they promote."
Vachon said Soros has pledged $1 million to American Bridge 21st Century, a "super" political action committee, or Super PAC, that is largely focused on research and tracking Republican candidates.
Soros, one of the biggest donors to liberal groups, also will give another $1 million to America Votes, an organization that helps coordinate campaign-related activities for liberal groups nationwide.
"Both groups are part of a progressive infrastructure, or center-left establishment, that plays an increasingly important role in elections," Vachon said.
Super PACs are fundraising organizations that operate independently from individual candidate's campaigns and can raise unlimited amounts from individuals, corporations and unions and spend to support candidates or issues.
Soros for months has remained on the sidelines of the Super PAC frenzy that has marked the 2012 campaign. Super PACs have been raking in unlimited amounts of money from wealthy individuals.
But many Democratic givers staunchly opposed them and have not participated, giving Republicans a fundraising edge. Democratic fundraisers and groups, however, have said that other donors were watching for a signal from Soros before deciding whether to jump in.
Last year, Soros gave $100,000 to Majority PAC, a Super PAC helping Democratic Senate candidates. He also gave $75,000 to House Majority PAC, another Super PAC that focuses on putting Democrats in the House of Representatives.
In the 2004 elections, Soros was the biggest donor to the Super PAC predecessors, the so-called "527" groups. Those tax-exempt organizations were forbidden from "expressly advocating" for the election or defeat of specific candidates.
(Reporting Alina Selyukh; Editing by Philip Barbara)