ROCK HILL, S.C. (AP) -- The Democratic primary race entered a new phase on Friday night, with Vermont Sen. Bernie Sanders and former Gov. Martin O'Malley escalating their criticism of front-runner Hillary Rodham Clinton.
With her numbers on the rise after a summer slump, Clinton finds herself increasingly targeted by her primary opponents --- a tonal shift for a race that has been notably civil for much of the early primary.
But in South Carolina on Friday night, there was a bit less Southern gentility on display.
In individual interviews with MSNBC host Rachel Maddow, both Sen. Bernie Sanders and former Gov. Martin O'Malley cast themselves as the party's liberal standard-bearers, questioning Clinton's commitment to the causes Democrats hold dear.
Though careful never to mention Clinton by name, Sanders drew a sharp contrast with her on everything from campaign finance reform to foreign affairs.
He noted his opposition to the war in Iraq and his refusal to accept super PAC donations and said he opposes the Obama administration's recent decision to send special forces to Syria, a position that Clinton supports. He also undermined Clinton's opposition to the Keystone XL pipeline, which was officially rejected by President Barack Obama's administration hours earlier after a yearslong campaign by liberal activists.
Clinton said she opposed the pipeline in September, a project she said she was "inclined" to support back in 2010 as President Barack Obama's secretary of state.
"For me, as opposed to some other unnamed candidates, the issue of Keystone was kind of no brainer," he said. "I said to no to Keystone on Day One."
O'Malley echoed his critique, adding in his own shots at Sanders. In an effort to break into what's shaping up to be a two-person primary race, he suggested that the self-identified democratic socialist is not a loyal member of the party.
"I think that when President Obama was running for re-election, I was glad to step up and work very hard for him while Sen. Sanders was trying to find someone to primary him," O'Malley said. "I'm a Democrat. I'm a lifelong Democrat. I'm not an independent. I'm not a former Republican. I believe in the party of Franklin Roosevelt."
The offensive comes little more than a week before the candidates will meet in Iowa for their next debate, a forum Clinton showed a commanding control of during the first match-up last month.
The message intended for Democratic voters was clear: Clinton cannot be trusted to fight hard for liberal values.
Clinton, who followed the two men on the stage, largely stuck to her campaign themes, never acknowledging either of her opponents, But she cast herself as a fighter for liberal principles, demurring when asked whether she's the most hawkish of the Democratic hopefuls and vowing to take on the Koch brothers.
"Anybody who thinks they can influence what I will do doesn't know me very well," she said, responded to a question about the millions of dollars she made from highly paid speeches to Wall Street bankers.
Democrats have spent months boasting about the substantive tone of their contest, attempting to set-up a favorable early contrast with the crowded and often carnival-like insults of the Republican primary.
Sanders, in particular, has vowed to avoid character attacks, making an intense focus on policy a key part of his insurgent rise. With his more aggressive approach toward Clinton, Sanders risks undermining his outsider brand by sounding like he's practicing politics as usual.
His aides insist that that he has not made a dramatic shift to draw sharper contrasts with Clinton.
"It's not about punching up," campaign manager Jeff Weaver told reporters after the event.
But while Sanders blamed the media, saying he can't walk through the U.S. Capitol without reporters "begging me to attack Hillary Clinton," there's little question he's sharpened his critique in recent days.
After seeming to set aside the issue of what he described as her "damn emails" in the first Democratic debate, he appeared to reopen the saga in an interview with The Wall Street Journal earlier this week, saying there are "valid questions" about her correspondence. Aides say he hasn't changed his position, arguing he long backed continuing the federal investigation into her use of a private server.
And he was blunt in a Boston Globe editorial meeting on Thursday: "I disagree with Hillary Clinton on virtually everything," he said.
A day later, Sanders insisted that his comments are rooted not in personality politics but serious policy differences.
"I would not have run for president," he said, "if I believed that establishment politics and establishment economics could solve the very serious problems that we face."
The forum, sponsored by MSNBC, kicks off a weekend of Democratic events in South Carolina, which hosts the South's first presidential primary weeks after Iowa and New Hampshire begin the nominating process. South Carolina is particularly important for Democrats, because it is the first state where black voters --- a key part of Obama's coalition in his two victories --- will comprise a significant portion of the electorate.