Donald Trump is set to get a huge opportunity to make the U.S. Supreme Court more staunchly conservative, after crucial swing vote Justice Anthony Kennedy announced his plans to retire this today. For three decades, he has functionally been one of the most powerful people in American politics.

“It has been the greatest honour and privilege to serve our nation in the federal judiciary for 43 years, 30 of those years on the Supreme Court,” Justice Kennedy said in a statement.

Of the current nine Supreme Court justices, Kennedy is considered a traditional conservative – but his willingness to side with the liberal judges on crucial cases has meant that he is considered something of a ‘swing vote’ and has therefore not been reliable to America’s right-wing in enacting their agenda. For example, Kennedy was the vote which edged same-sex marriage over the line and made it legal in all 50 states.

He also affirmed Roe v Wade, the political decision which made abortion legal nationwide, back in 1992 – much to the annoyance of U.S. conservatives.

On the other hand, he also also allowed the passage of conservative legislation. He signed off on Trump’s travel ban last week, edging it past liberal opposition, and was also a key voice in the Citizens United ruling back in 2010, which gave corporations untrammelled power to pour money into political communication.

Trump immediately confirmed that he has begun the search for a new justice, having narrowed it down to a shortlist of 25 candidates. It’s guaranteed he is going to pick a conservative who will then help form a solid (and dominant) voting bloc on the Supreme Court. For progressives, this will be unimaginably bad.

Trump has already been able to select one Supreme Court justice: Neil Gorsuch, who replaced fellow conservative Antonin Scalia after his death. Scalia actually died during Barack Obama‘s tenure, but Republicans were successful in blocking Obama’s liberal nomination to the Court, Merrick Garland.

Of everything Trump has done so far, successfully securing a reliable conservative majority on the Supreme Court would be the most consequential. Justices remain on the Supreme Court until they die or step down, meaning that a conservative-leaning court will be making decisions for a long, long time.

A slight reassurance is that the principle of stare decisis means that existing liberal rulings are unlikely to be struck down unless there is a compelling reason to revisit them. But that’s absolutely not rock-solid, and it leaves to be seen what a Trump-stacked Supreme Court might end up doing.

So that’s that. Ooft.

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