Bernie Sanders is escalating his attacks on Hillary Clinton — and Trump is taking notes

bernie sanders
bernie sanders

(Joe Raedle/Getty Images)
Bernie Sanders.

Sen. Bernie Sanders is planning on taking his presidential bid all the way to the Democratic National Convention in Philadelphia this summer.

And it looks like his rhetorical shots at Democratic presidential rival Hillary Clinton will go with him.

Leading up to Indiana's primary on Tuesday, Sanders has proved more than willing to continue drawing contrasts with Clinton on major issues.

During a Monday campaign rally in Indiana, Sanders reiterated his usual attacks on Clinton's campaign-finance structure, pausing for boos and cracking jokes about Clinton's private speeches to Goldman Sachs.

"We said, 'Hell no' to super PACs. We don't represent Wall Street or the billionaire class," Sanders said.

He added: "Secretary Clinton has chosen another approach to raise her money. She has not one but several super PACs. In the last reporting period, her major super PAC reported raising $25 million from special interests, including $15 million from Wall Street."

For a moment late last month, it appeared that Sanders might dial back his attacks against his rival, as Clinton's lead in the Democratic race expanded with big victories in primaries in New York and up and down the East Coast.

Speaking to The New York Times last week, senior campaign strategist Tad Devine said that the Sanders campaign would "reassess" its strategy after a string of recent losses. Some political observers noted that the campaign made no mention of Clinton in a statement following Sanders' losses, indicating that he might have been preparing to shift from his rhetorical focus on the frontrunner.

But people close to the campaign have maintained that Sanders is serious about his pledge to participate in a "contested convention." He also reiterated the vow during a Sunday press conference.

Meanwhile, Sanders has continued to cast doubt on the legitimacy of the Democratic presidential-selection process.

On Monday, Sanders used Clinton's massive lead among Democratic superdelegates — elected officials and party officials who represent a small portion of the delegates needed to clinch the nomination — to illustrate how a "rigged system" was built to stymie insurgent candidacies. He again reminded superdelegates that he polls better in hypothetical general-election matchups with Republican frontrunner Donald Trump.

Speaking to supporters on Monday, Sanders reflected on the opposition that his campaign faced in the past year from many Democrats.

"We were taking on the entire Democratic Party establishment," Sanders said, as the audience cheered. "Looks like you're not intimidated by the establishment."