Justice Anthony Kennedy, far right; photo via the White House

A shake-up in the Supreme Court has triggered what could be the most heated partisan battle of Trump’s already contentious tenure. After upholding Trump’s controversial travel ban on Tuesday, Justice Anthony Kennedy submitted his resignation the next day — opening a Supreme Court vacancy that could potentially shape American politics for decades.

According to the New York Times, Justice Kennedy, 81, handed Trump his walking papers on Wednesday, expressing gratitude for his years serving the American public. Originally appointed by President Ronald Reagan, Justice Kennedy stepped over partisan lines frequently throughout 30 years on the bench. Despite support for conservative campaign finance laws and loose gun regulations, Kennedy was instrumental in legalizing same-sex marriage in 2015 and has supported abortion rights at every turn.

Now that Kennedy has announced his resignation, President Trump has indicated that he will nominate a strongly conservative replacement, potentially creating a 5-4 right-wing majority with no justices willing to break from party lines.

Less than two years into his first term, Trump has already appointed one Supreme Court Justice — Neil Gorsuch. During the process of selecting Gorsuch, Trump and his advisors compiled a list of 25 conservative judges, and the president has already said he will use that same list to select Kennedy’s replacement as well.

“We have a very excellent list of great, talented, highly educated, highly intelligent — hopefully, tremendous — people. I think the list is very outstanding,” Trump said Wednesday. “So it will be somebody from that list.”

But despite a Republican-led Senate that could confirm any presidential nominee with a simple majority vote, Democratic lawmakers have sprung into action to either delay or entirely block Trump’s selection. Citing precedent set by Senate Majority Leader Mitch McConnell in 2016 — when Senate Republicans blocked President Obama from appointing Merrick Garland to replace deceased Justice Antonin Scalia — Democratic Senate leader Chuck Schumer told his fellow legislators Thursday that, “People are just months away from determining the senators who should vote to confirm or reject the president’s nominee, and their voices deserve to be heard now, as Senator McConnell thought that they deserved to be heard then.”

Out of Trump’s list of 25 potential nominees, the New York Times has singled out federal appellate judge Brett M. Kavanaugh and Judge Thomas M. Hardiman, a current member of the federal Third Circuit Court of Appeals, as frontrunners for the forthcoming nomination.

With enough Republican power in the Senate to confirm a potential judge without any Democratic approval, leftist legislators are looking towards other avenues of delay, including advertising campaigns and research initiatives to discredit any advanced nominees.

“There are people who have had to withdraw over the years because you get information out and you question them and the public is focused on it and galvanized by it,” Democratic Senator Amy Klobuchar, told the Times.

But if those attempts are unsuccessful, Democrats in Washington are pulling no punches when they describe Kennedy’s open seat as a potential disaster for the issues of same-sex marriage, abortion rights, and other Supreme Court rulings that make up the fabric of American society.

“I think it has sunk in very quickly that this is the biggest fight of them all,” Brian Fallon, a veteran Democratic operative with the organization Demand Justice, told the Times. “If we don’t succeed in this fight, Trumpism will be here for 40 years, not just four years.”