“The Democratic Party isn’t going back to the days of welfare reform and the crime bill,” she said, highlighting measures Mr. Clinton signed into law as president that are reviled by much of the left. “It is not going to happen.”

Yet Ms. Warren, a Massachusetts Democrat who is widely thought to be considering running for president in 2020, noted to about 1,000 activists here for the yearly Netroots Nation meeting that they hardly needed to worry about the party shifting to the middle as it did in the 1990s. Liberals, she said, have taken charge.

“We are not the gate-crashers of today’s Democratic Party,” Ms. Warren said, invoking a term first used to describe the liberal blogosphere that emerged a decade ago. “We are not a wing of today’s Democratic Party. We are the heart and soul of today’s Democratic Party.”
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Ms. Warren lampooned a recent New York Times opinion article, “Back to the Center, Democrats,” by the onetime Clinton strategist Mark Penn and the former New York City Council president Andrew Stein. “The path forward is to go back to locking up nonviolent drug offenders and ripping more holes in our economic safety net,” she said of their argument.
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“If we’re going to be the people who lead the Democratic Party back from the wilderness and lead our country out of this dark time, then we can’t waste energy arguing about whose issue matters more or who in our alliance should be voted off the island,” she said, drawing applause.