Hillary Clinton has a message for Republicans bemoaning the rise of Donald Trump: “You reap what you sow.”

In a speech on Monday, the former secretary of state blamed Republicans’ obstructionism, which she said fomented Trump’s incendiary campaign.

“Donald Trump didn’t come out of nowhere,” Clinton said in a speech at the University of Wisconsin-Madison. “What Republicans have sown with their extremist tactics, they’re now reaping with Trump’s candidacy.”

“Once you make the extreme normal, you open the door to even worse,” she added.

In the speech, Clinton asked voters to consider – “as scary as it might be” – who Trump might pick to fill the supreme court vacancy after the death of Justice Antonin Scalia in February. The president has nominated Judge Merrick Garland, but Republican leadership has refused to even grant him a hearing.

Clinton singled out Senate judiciary committee chairman Chuck Grassley of Iowa who, along with Senate majority leader Mitch McConnell of Kentucky, have committed to keeping Garland from having a hearing. The Republicans have argued that the next president should pick Scalia’s replacement on the bench. She quoted Grassley, who has said that allowing Obama to pick the nominee is in effect denying voters a voice in shaping the supreme court.

“As one of the more than 65 million Americans who voted to re-elect Barack Obama, I’d say my voice is being ignored,” Clinton argued. Then, she said: “I’m adding my voice to the chorus asking Senator Grassley to step up and do his job. He should hold a hearing.”

In the speech, Clinton articulated why she believed Democrats should make the supreme court vacancy a voting issue, noting that the next president will likely make two or three more additional nominations to the bench during the next four years. Clinton invoked the seminal 1965 supreme court case Griswold v Connecticut that effectively decided a woman’s right to use birth control. A young high school student at the time, Clinton said the case underscored the role the nation’s highest court played in expanding – or restricting – the rights of America’s most vulnerable and marginalized people.

“For a long time now the ideological bent of the court has led our country in the wrong direction, stacking the deck in favor of the wealthy and powerful,” Clinton said. She promised to appoint justices who would expand civil and human rights, and cited the supreme court’s role in legalizing same-sex marriage.

“That decision is the latest reminder of what the court can do when it stands for equality, or against it. When it makes America a fairer place, or rolls back the progress we’ve worked so hard to achieve,” she said. “It depends on what the court decides, and it depends on who’s deciding.”

Clinton is campaigning in Wisconsin ahead of the state’s primary on 5 April, where she will try to end Bernie Sanders’ hot streak. The senator from Vermont has picked up momentum after winning five out of the past six Democratic nominating contests.

His string of victories over the weekend has erupted into a testy exchange between the Democratic rivals, whose campaigns held dueling press calls on Monday, over whether Sanders has a viable path forward.

“While Hillary Clinton is the clear frontrunner … she has emerged as a weak frontrunner,” Sanders’ strategist Tad Devine told reporters on a conference call on Monday. Hours later, Clinton’s top strategist, Joel Benenson, told reporters that the former secretary of state’s lead was “nearly insurmountable” and that there “simply is not enough real estate left” for Sanders to close the pledged-delegate gap.