(Recasts with Working Families Party endorsement)
By David Shepardson and Joseph Ax
WASHINGTON/NEW YORK, Sept 16 (Reuters) - Democratic presidential candidate Elizabeth Warren on Monday won the endorsement of the Working Families Party, a progressive group with growing political influence that previously backed U.S. Senator Bernie Sanders during his 2016 White House bid.
The group's endorsement of Warren, a U.S. senator from Massachusetts, reflected its belief that "sitting on the sidelines" during the Democratic nominating contest is not the best way to beat Republican President Donald Trump in November 2020, said Maurice Mitchell, national director of the Working Families Party.
The organization's thousands of dues-paying members voted to endorse after interviewing five of the 20 Democratic candidates: Warren, Sanders, former U.S. housing chief Julián Castro and New York City Mayor Bill de Blasio. Their backing of Warren comes as opinion polls show her gaining ground against the contest's front-runner, former Vice President Joe Biden, a more moderate candidate.
Warren got nearly 61% of members' votes, while Sanders drew almost 36% support.
Mitchell said progressive voters face a "tough choice" this year but that "Elizabeth Warren is offering an agenda of real structural change."
Warren wrote on Twitter that she was "grateful" for the Working Families Party's endorsement. "Together, we're going to make the big, structural change we need so that government works for all of us - not just the wealthy and well-connected," she said.
The endorsement came ahead of Warren's campaign rally in New York City on Monday evening, an event expected to draw thousands as she delivers a speech on corruption in Washington.
Earlier on Monday, Warren proposed a major rewrite of U.S. laws governing lobbying that she said was aimed at restricting corporate influence and rooting out corruption. In the detailed plan, Warren proposed barring elected officials and senior government appointees from ever becoming lobbyists.
She would also ban U.S. firms from lobbying on behalf of foreign governments, expand the definition of lobbyists to include anyone paid to influence lawmakers, impose new taxes on excessive lobbying by large companies and restrict the ability of industry officials to "dominate" the regulatory process.
The Center for Responsive Politics said in January that companies and others spent $3.42 billion on lobbying in 2018, the highest amount in eight years.
Warren's plan takes aim at Trump, a real estate developer who as president regularly visits his own hotels, resorts and golf clubs. She would require presidents and vice presidents to place business assets in a blind trust to be sold and require other senior officials to divest assets that could present conflicts.
Trump maintains ownership of his businesses but has ceded day-to-day control to his sons. Last week, Trump, who has refused to release his personal tax returns, said that before November 2020, he would release an "extremely complete" financial report.
Warren noted that T-Mobile US Inc, which won Justice Department approval to merge with Sprint Corp in July, "sent its top executives to the Trump Hotel in DC right after the company announced a merger."
On Friday, a federal appeals court revived a lawsuit alleging that Trump violated the U.S. Constitution by profiting from foreign and domestic officials who patronized his properties. Trump denies the allegations.
Warren wants to ban lobbyists from all fundraising activities, including hosting events or serving as campaign bundlers, bar senior officials and members of Congress from trading individual stocks and pay congressional staff salaries "competitive" with the private sector. She would bar all federal employees from becoming corporate lobbyists for six years after leaving government.
She would also prohibit courts from using sealed settlements to conceal evidence in cases involving public health or safety and allow the public to sue federal agencies to enforce rules.
Warren cited General Motors Co's decision more than a decade ago to settle some cases involving deadly ignition switch defects on the condition the terms remain confidential. (Reporting by David Shepardson in Washington and Joseph Ax in New York City; additional reporting and writing by Amanda Becker in Washington; Editing by Colleen Jenkins, Peter Cooney and Dan Grebler)