(Democratic presidential candidate Hillary Clinton and US vice-presidential nominee Tim Kaine stand on stage at the end on the fourth day of the Democratic National Convention.Alex Wong/Getty Images)

PHILADELPHIA — Following a dark and occasionally rocky Republican convention in Cleveland last week, Democratic planners wanted to strike a different, more harmonious note.

But as raucous protesters shouted over convention speakers and refused to fully embrace the call for unity, some Democratic lawmakers began making an argument familiar to audiences watching the Republican national convention: Think about the Supreme Court.

On Tuesday, Ohio Gov. Ted Strickland predicted that Sen. Bernie Sanders' former supporters will coalesce around Hillary Clinton once they realize that Donald Trump's election could put several conservative justices on the court.

"If one or two or three or four young, radical conservative people were placed on that court, everything the Bernie supporters care about would be at risk," Strickland told Business Insider at an event with climate activists. "If they have a brain and really thought it through — I'm sure they do have brains, they’re bright people — they would understand the consequences of pulling back and not getting on board with Secretary Clinton."

Speaking on a panel on Wednesday, Rep. Keith Ellison urged holdout Sanders supporters to envision what the court would be like if Al Gore would've beaten George W. Bush in the 2000 election, appointing liberal supreme court justices.

"This is a very serious situation that we're in," said Ellison, one of Sanders' most high-profile supporters in Congress.

"The stakes couldn't be higher when it comes to the Supreme Court. From a constitutional standpoint — if you supported Bernie, if you believe in a fair economy, if you believe in criminal justice ... then there's not way you're going to let Donald Trump become president."

Many Democrats say that raising awareness of Senate Republicans' refusal to allow hearings to fill the Supreme Court vacancy left when Supreme Court Justice Antonin Scalia died is a winning strategy. Hart Research, a polling group that conducts surveys for Clinton-aligned groups, found in a June survey that 50% of voters said replacing Supreme Court justices was a very important consideration in their presidential vote, up from 30% in 2012.

Further, recent surveys conducted by Public Policy Polling showed that many voters in swing states like Iowa, New Hampshire, and Pennsylvania don't trust Trump to fill the vacancy.

Earlier this year, the Republican presidential nominee released a list of candidates he would consider to fill the Supreme Court vacancy. Many Republicans lauded the potential choices, many of which came straight off a list of potential nominees compiled by the conservative think tank the Heritage Foundation.