Story highlights The announcement is yet another overture to the wing of the party that is loyal to Vermont Sen. Bernie Sanders

She will tell an audience Saturday at Netroots Nation that a key way to restore order to politics is to curb unaccounted money

(CNN) Hillary Clinton will pledge on Saturday to introduce an amendment to the Constitution to overturn the Supreme Court's Citizen United decision within the first 30 days of her administration, an aide said Saturday.

Clinton first made the pledge to overturn the 2010 Supreme Court decision Citizens United, which opened the floodgates for outside money in politics, while campaigning in Iowa in 2015. She will tell an audience Saturday in a video to be played at Netroots Nation, a liberal organizing conference in St. Louis, that a key way to restore order to politics is to curb unaccounted money.

A Clinton aide said the plan was a "a key plank of Clinton's plan to challenge the stranglehold that wealthy interests have over our political system" and would allow "Americans to establish common sense rules to protect against the undue influence of billionaires and special interests and to restore the role of average voters in elections."

Organizations focused on getting unaccounted money out of politics heralded Clinton's planned announcement.

"Hillary Clinton's commitment to overturning Citizens United, and her other systemic proposals like public financing of congressional elections, are key to improving our chances of victory on every other issue. It's great that she elevated progressive infrastructure by making this announcement at Netroots Nation -- and that she is promising to elevate the fight against big money influence in politics during her first month in office," said Marissa Barrow, a spokeswoman for the Progressive Change Campaign Committee.

Read More