Warren, Sanders attacked over liberal policies in 2nd debate

The two top-ranked candidates are feisty US senators and close friends who have built grass roots movements and advocate similar left-leaning agendas.

Warren immediately demanded "big, structural change" and warned that political "spinelessness" against President Donald Trump will leave intact a "rigged system that has helped the wealthy and well-connected and kicked dirt in the faces of everyone else." But she and Sanders faced crisp and immediate pushback from a handful of moderates challenging their call for such dramatic change in the US economy, particularly in health care.

"We have a choice. We can go down the road that Senator Sanders and Senator Warren want to take us, with bad policies like Medicare for All, free everything, and impossible promises that will turn off independent voters and get Trump re-elected," ex-congressman John Delaney said in a scathing early criticism of his liberal rivals.

The debate features 20 candidates over two nights in Detroit, Michigan, a battleground state that Trump snatched from Democrats in 2016.

Frontrunner Joe Biden takes the stage Wednesday between senators Kamala Harris and Cory Booker, prominent African American candidates who have strongly criticized the former vice president on racial issues.

The stakes are sky high. The debate is likely to winnow the sprawling field, perhaps by as much as half, ahead of the next one in September as the party seeks its best nominee to challenge Trump.

Underperformers like Senator Amy Klobuchar and Colorado ex-governor John Hickenlooper, both polling at under two percent, scrambled for breakout moments that resonated enough with voters to keep their struggling campaigns alive.

Without one, several lower-tier candidates will have little justification for staying in the race.

Biden has managed to maintain his pole position, with around 32 percent support according to a poll average compiled by RealClearPolitics.com.

Warren and Sanders are essentially tied for second, at about half Biden's support.

With major appeal among the party's liberal wing, Warren and Sanders share similar political platforms: both support universal health care, tuition-free public college, tax hikes on the wealthiest Americans, a USD 15-per-hour minimum wage and aggressive regulations on Wall Street.

But while Sanders is a self-proclaimed Democratic socialist seeking to whip up a "political revolution," Warren calls herself a capitalist who advocates fixes to the existing structure, including strict regulations on US markets.

Critics warn of the risks of driving the party too far leftward ahead of the election.

As Warren and Sanders sold their liberal prescriptions, several moderates on stage Tuesday urged more centrist approaches.

"I share their progressive values, but I'm a little more pragmatic," Hickenlooper said.

The Detroit showdown was expected to bring more heat than last month's opener, in part because of the expected clash between Biden, Harris and Booker.

With Harris smelling blood, and Booker needing a viral moment to keep his candidacy alive, Wednesday fireworks are likely.

And Trump's recent disparaging comments about the city of Baltimore and a black member of Congress will no doubt intensify Democrats' talk about America's troubled racial legacy.

But Trump also gave Biden, under fire for touting his work with segregationists and opposing federal busing policies aimed at desegregating schools decades ago when he was a US senator, an opening to point to the president as the target of Democratic anger over racial injustice.

After his lackluster June performance when he faced withering criticism from Harris, Biden acknowledged he was ill-prepared to counter the brickbats, but would not be as polite in the second round.