Justice Anthony M Kennedy, a pivotal swing vote on the Supreme Court, has announced his plans to retire. This means President Donald Trump has the chance to dramatically shift the ideology of America’s highest court to the right.

Justice Kennedy’s departure sets the stage for what is likely to become a bitter partisan fight over his confirmation, with Democrats in the Senate likely to pull all the stops to try and influence who ultimately replaces the departing conservative.

“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, who will vacate his seat on 31 July, said in a statement.

Justice Kennedy had told Mr Trump that he was leaving the court separately, in a letter in which expressed gratitude for having had the opportunity to serve the United States’ highest court.

“My dear Mr President,” he wrote. “For a member of the legal profession it is the highest of honour to serve on this court. Please permit me by this letter to express my profound gratitude for having had the privilege to seek in each case how best to know, interpret and defend the Constitution and the laws that must always conform to its mandates and promises”.

His departure leaves many questions about the future of the court.

Supreme Court strikes down abortion restrictions Show all 23 1 /23 Supreme Court strikes down abortion restrictions Supreme Court strikes down abortion restrictions Abortion rights activists hold placards outside of the US Supreme Court ahead of an expected ruling on abortion clinic restrictions on June 27, 2016 in Washington, DC. Mandel Ngan/AFP/Getty Supreme Court strikes down abortion restrictions An abortion rights activist holds placards outside of the US Supreme Court before the Court struck down a Texas law placing restrictions on abortion clinics on June 27, 2016 in Washington, DC. The US Supreme Court on Monday struck down a Texas law placing a raft of restrictions on abortion clinics, handing a major victory to the "pro-choice" camp in the country's most important ruling on the divisive issue in a generation. Mandel Ngan/AFP/Getty Supreme Court strikes down abortion restrictions WASHINGTON, DC - JUNE 27: Pro-life activists pray on the steps of the United States Supreme Court on June 27, 2016 in Washington, DC. In a 5-3 decision, the U.S. Supreme Court struck down one of the nation's toughest restrictions on abortion, a Texas law that women's groups said would have forced more than three-quarters of the state's clinics to close. Pete Marovich/Getty Supreme Court strikes down abortion restrictions WASHINGTON, DC - JUNE 27: Texas abortion provider Amy Hagstrom-Miller looks on as Nancy Northup, President of The Center for Reproductive Rights speaks to the media outside of the U.S. Supreme Court on June 27, 2016 in Washington, DC. In a 5-3 decision, the U.S. Supreme Court struck down one of the nation's toughest restrictions on abortion, a Texas law that women's groups said would have forced more than three-quarters of the state's clinics to close. Pete Marovich/Getty Supreme Court strikes down abortion restrictions An abortion rights activist holds placards outside of the US Supreme Court before the Court struck down a Texas law placing restrictions on abortion clinics on June 27, 2016 in Washington, DC. The US Supreme Court on Monday struck down a Texas law placing a raft of restrictions on abortion clinics, handing a major victory to the "pro-choice" camp in the country's most important ruling on the divisive issue in a generation. Getty Supreme Court strikes down abortion restrictions Texas abortion provider Amy Hagstrom-Miller wipes a tear as she walks down the steps of the United States Supreme Court with Nancy Northup, President of The Center for Reproductive Rights on June 27, 2016 in Washington, DC. In a 5-3 decision, the U.S. Supreme Court struck down one of the nation's toughest restrictions on abortion, a Texas law that women's groups said would have forced more than three-quarters of the state's clinics to close. Pete Marovich/Getty Supreme Court strikes down abortion restrictions Abortion rights activists cheer after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. Mandel Ngan/AFP/Getty Supreme Court strikes down abortion restrictions Abortion rights activists cheer after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. Mandel Ngan/AFP/Getty Supreme Court strikes down abortion restrictions WASHINGTON, DC - JUNE 27: Abortion rights activists Morgan Hopkins of Boston, left, and Alison Turkos of New York City, celebrate on the steps of the United States Supreme Court on June 27, 2016 in Washington, DC. In a 5-3 decision, the U.S. Supreme Court struck down one of the nation's toughest restrictions on abortion, a Texas law that women's groups said would have forced more than three-quarters of the state's clinics to close. Pete Marovich/Getty Supreme Court strikes down abortion restrictions Abortion rights activists cheer after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. Getty Supreme Court strikes down abortion restrictions WASHINGTON, DC - JUNE 27: Abortion rights activists Morgan Hopkins of Boston, left, and Alison Turkos of New York City, celebrate on the steps of the United States Supreme Court on June 27, 2016 in Washington, DC. In a 5-3 decision, the U.S. Supreme Court struck down one of the nation's toughest restrictions on abortion, a Texas law that women's groups said would have forced more than three-quarters of the state's clinics to close. (Photo by Pete Marovich/Getty Images) Getty Images Supreme Court strikes down abortion restrictions Abortion rights activist Morgan Hopkins of Boston, celebrates on the steps of the United States Supreme Court on June 27, 2016 in Washington, DC. In a 5-3 decision, the U.S. Supreme Court struck down one of the nation's toughest restrictions on abortion, a Texas law that women's groups said would have forced more than three-quarters of the state's clinics to close. Pete Marovich/Getty Supreme Court strikes down abortion restrictions Abortion rights activists embrace after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. AFP/Getty Images Supreme Court strikes down abortion restrictions Abortion rights activists hold placards outside of the US Supreme Court ahead of a ruling on abortion clinic restrictions on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. Mandel Ngan/AFP/Getty Supreme Court strikes down abortion restrictions In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. Mandel Ngan/AFP/Getty Supreme Court strikes down abortion restrictions Abortion rights activists cheer after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. AFP/Getty Images Supreme Court strikes down abortion restrictions Abortion rights activists cheer after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. / AFP / MANDEL NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images) AFP/Getty Images Supreme Court strikes down abortion restrictions Abortion rights activists cheer after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. / AFP / MANDEL NGAN (Photo credit should read MANDEL NGAN/AFP/Getty Images) AFP/Getty Images Supreme Court strikes down abortion restrictions Abortion rights activists embrace after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. AFP/Getty Images Supreme Court strikes down abortion restrictions Pro-choice activist, Alissa Manzoeillo, of Washington, D.C. waits for rulings in front of the U.S. Supreme Court on June 27, 2016 in Washington, DC. A ruling is expected in Whole Woman's Health v. Hellerstedt, a Texas case the places restrictions on abortion clinics, as well as rulings in the former Virginia Governor's corruption case and a gun rights case. Pete Marovich/Getty Supreme Court strikes down abortion restrictions Abortion rights activists cheer after the US Supreme Court struck down a Texas law placing restrictions on abortion clinics, outside of the Supreme Court on June 27, 2016 in Washington, DC. In a case with far-reaching implications for millions of women across the United States, the court ruled 5-3 to strike down measures which activists say have forced more than half of Texas's abortion clinics to close. Supreme Court strikes down abortion restrictions Abortion rights activists hold placards outside of the US Supreme Court ahead of an expected ruling on abortion clinic restrictions on June 27, 2016 in Washington, DC. AFP/Getty Images Supreme Court strikes down abortion restrictions Abortion rights activists hold placards outside of the US Supreme Court ahead of an expected ruling on abortion clinic restrictions on June 27, 2016 in Washington, DC. AFP/Getty Images

Who is Justice Kennedy?

Justice Kennedy, 81, is the senior associate justice of the Supreme Court, having been on the court's bench longer than any of the other seven associates. Justice Kennedy was nominated to the post by former President Ronald Reagan in 1987. He was confirmed unanimously by the Senate in February of 1988.

Before that, Justice Kennedy served on the US Ninth Circuit Court of Appeals, a position he was appointed to by former President Gerald Ford in 1975.

How has he voted on the Supreme Court?

During his tenure on the court, Justice Kennedy became known as a pivotal swing vote amid the court’s split of four liberal and four other conservatives.

He has sided with liberal interests on some defining issues, and is known for letting conservatives down by upholding the basic underpinnings of Roe v Wade, a decision that guaranteed women the right to an abortion. Justice Kennedy also wrote the court’s biggest gay rights decisions, including a 2015 ruling that said the Constitutions protects the rights for gay people to get married, known as Obergefell v Hodges.

But, he has sided with conservatives more frequently, and swung further to the right on some of those issues than even some of the most conservative members of the court.

Justice Kennedy has held the view that the entirety of the Affordable Care Act — or Obamacare — is unconstitutional, and has upheld protective views of business. He also wrote the landmark opinion in Citizens United — which opened the floodgates on political fundraising that has resulted in a massive deluge of political giving in the United States.

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What is the Supreme Court?

The Supreme Court is tasked with interpreting the law, and is the final say on whether bills passed and sign by the legislative - Congress - and executive - presidential - branches are in line with the constitution.

The court is specifically created in the US Constitution as a check on those two branches of government, and hears some of the most consequential court decisions on a range of issues facing the nation.

That includes social and free speech issues — interpreting civil rights protections, or women’s constitutional access to abortion, for instance — as well as broader cases involving issues related to taxation — as has been the case with attacks on Obamacare.

Why is Justice Kennedy’s retirement important?

The retirement comes less than two years into Mr Trump’s term, with the president already having left an imprint on the court. Mr Trump restored its 5-4 conservative majority with the appointment of Justice Neil Gorsuch last year after the president's fellow Republicans in the Senate in 2016 refused to consider former Democratic President Barack Obama's nominee, Merrick Garland.

The latest nomination will come just before US citizens will have the opportunity to take part in their first nationwide vote during Mr Trump's term. The midterm elections in November could potentially reshape the configuration of the Senate and House of Representatives, with the Democrats looking to retake control of both sides of Congress from the Republicans.

The Senate is primarily important in that calculus, as the legislative body is in charge of confirming the president’s nominees for the court.

Beyond that, Justice Kennedy’s successor could have a significant impact on the ideological balance of the court. Since he has been seen as the swing vote on the court — especially on social issues — the nomination of a justice who swings further left, or disagrees with decisions related to abortion or civil rights, could have a major impact on the lives of the American people.

Plus, Supreme Court placements are life-long appointments — with very few, and unlikely, exceptions. Mr Trump could pick a young conservative would could sit on the powerful bench for decades to come.

What will Trump do now?

Mr Trump must now pick a replacement for Mr Kennedy, and he is said to be considering a list of 25 possible nominees.

Some analysts and observers expect the new nomination to come with in the next couple of weeks. The president will undoubtedly try to rush a confirmation through the Senate before the midterm elections.

Senate Majority Leader Mitch McConnell promised that the Senate would move swiftly on any nomination Mr Trump brings forward.

“We will vote to confirm Justice Kennedy’s successor this fall”, Mr McConnell said on the Senate floor just after the resignation was announced.

That 25 person list includes mostly state Supreme Court Justices from generally conservative states and US circuit court judges. One US senator is said to be on the list, Mike Lee of Utah.

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What could change?

That’s the crucial question, and a lot of that depends on who Mr Trump chooses to replace Justice Kennedy, and how that person ultimately acts on the Supreme Court.

It’s likely that Mr Trump will at least choose someone who aligns with conservative business interests, but the bigger question is how the future justice rules on social issues that have been massively contentious in the US.

Some cases have become touchstone issues for conservatives, and could be impacted,

The court could eventually overturn Roe v Wade, allowing states to ban most or all abortions.

The court could reject requests to overturn capital punishment rulings, and solitary confinement requests.

The court could ban governments from participating in race-based affirmative action programmes, which were enacted to help ensure that minorities are represented in the workplace and schools.