WASHINGTON (AP) — President Joe Biden on Monday proposed major changes for the U.S. Supreme Court: an enforceable code of ethics, term limits for justices and a constitutional amendment that would limit the justices' recent decision on presidential immunity.

There's almost no chance of the proposal passing a closely divided Congress with Election Day looming, but the ideas could still spark conversation with public confidence in the court hitting an all-time low in recent years amid ethical revelations about some justices. It also comes against the backdrop of a contentious presidential election and growing Democratic outrage about recent decisions from the conservative-majority court.

Here's a look at how the ideas, how they might work, and the possible stumbling blocks:

How would justices' terms be limited?

Limiting how long justices serve on the nation's highest court has broad support among Americans, polling indicates.

A poll from The Associated Press-NORC Center for Public Affairs Research in July 2022 found 67% of Americans support a proposal to set a specific number of years that justices serve instead of life terms, including 82% of Democrats and 57% of Republicans.

Biden's proposal would limit justices to 18-year terms, a system that he says would make nominations more predictable, less arbitrary, and reduce the chances that a single president could shape the court for generations to come.

There's a big problem: The Constitution gives all federal judges lifetime tenure.

There are ideas about how to impose term limits without an amendment — but if such a law passed and were challenged in court the justices could end up ruling on it.

How would a code of ethics be enforced?

The Supreme Court didn't have a formal code of ethics until last year, when the justices adopted one in the face of sustained criticism over undisclosed trips and gifts from wealthy benefactors to some justices, including Clarence Thomas.

It still lacks a means of enforcement — something Biden says is "common sense." Members of Congress, for example, generally can't accept gifts worth more than $50.

Anyone can file complaints against other federal judges, who are subject to censure and reprimand. Justice Elena Kagan voiced support for adding an enforcement mechanism to the Supreme Court ethical code in a public appearance last week.

Still, making the high court's ethical code enforceable raises thorny questions about how it might be enforced, and by whom.

Lower courts say their discipline process isn't intended to directly police their code of ethics, maintaining the code is too broadly phrased for violations to directly translate into discipline, said Charles Geyh, a law professor at Indiana University and expert in judicial ethics.

It's overseen by the Judicial Conference, which is headed up by Chief Justice John Roberts.

What about presidential immunity?

Biden is also calling for a constitutional amendment limiting the Supreme Court's recent decision giving former president Donald Trump — and all other presidents — broad immunity from criminal prosecution.

The amendment would "make clear that there is no immunity for crimes a former president committed while in office," Biden wrote in an opinion piece in the Washington Post. "We are a nation of laws — not of kings or dictators."

Constitutional amendments, though, have even higher hurdles than new laws. The proposal must get support from two-thirds of both the House and Senate and then be ratified by three-quarters of state legislatures.

No new amendments have passed in more than 30 years.

Biden has resisted other calls reform the Supreme Court

A former chairman of the Senate Judiciary Committee, Biden has long resisted calls to reform the Supreme Court.

In 2021, he fulfilled a campaign promise by convening a commission t o study potential changes to the court. It was not charged with making recommendations and cautioned that excessive change could potentially erode democracy.

There's been little movement on the issue until the latest proposals, which come amid growing outrage among Democrats about high court opinions that overturned landmark decisions on abortion rights and federal regulatory powers.

Even if Biden's proposals aren't likely to pass, the ideas could draw the attention of voters in a tight presidential election.

Conservative activist Leonard Leo blasted Biden's proposals in a statement: "It's about Democrats destroying a court they don't agree with."