Most Democratic presidential candidates have policy ideas that Republicans aren’t going to support. A growing number of them have a solution: Get rid of the Senate filibuster so a simple majority can pass legislation. Then you don’t have to worry about what Republicans think.

The latest example: If Republicans fail to act on climate change, said Sen. Kamala D. Harris (D-Calif.) at a CNN climate town hall Wednesday, “as president of the United States, I am prepared to get rid of the filibuster to pass a Green New Deal.” (Getting rid of the filibuster is something President Trump falls back on, too, when he’s frustrated with Congress.)

Except, undoing the filibuster is a lot easier said than done. It would probably take Democrats winning the White House and Senate and convincing a majority of Democratic senators to give up their last vestige of parliamentary power.

To understand why this is such a heavy lift, let’s start with a quick explanation of what the filibuster is.

It’s a centuries-old legislative tool that allows any senator to object to legislation and hold it up. It takes a supermajority, or 60 out of 100 senators, to overcome the filibuster and move on to a vote.

As Congress gets more partisan, the filibuster has turned into a powerful tool for the minority to block bills they oppose. Rarely these days does a major policy change automatically have 60 votes, and rarely these days does one party have 60 members in the Senate. As such, rarely these days do major policies pass the Senate. Right now, Republicans have a 53-47 majority.

So as the minority party ramps up use of the filibuster, the majority party has decimated it in recent years. There is no longer a way to filibuster presidential nominations to Cabinet posts and the courts, including the Supreme Court.

In 2013, Senate Democrats took the first historic step in this process by getting rid of the filibuster for judicial and political nominees except ones to the Supreme Court. It was such a dramatic move it was known in Washington as the “nuclear option.”

But it came with a high cost for Democrats.

In 2017, Republicans were in power, and they got rid of the filibuster for Supreme Court nominees. With a simple majority, they have been able to put on the Supreme Court two of the most controversial justices in modern memory, over Democrats’ vehement objections. But Democrats had laid the trip wire for this, and there was nothing they could do. The court under Trump is now tilted conservative for years.

The filibuster for legislation is still intact, but clearly the filibuster is on a slippery slope. In fact, it may only be a matter of time before the Senate gets rid of the filibuster for legislation, said Sarah Binder, a parliamentary expert with the Brookings Institution. “It's hard to put the toothpaste back in the tube,” she wrote in an email to The Fix.

But is that time now? Under no scenario I can think of would a Republican Senate get rid of the filibuster to help a Democratic White House. So first Democrats would have to win the Senate. They can do it, but they’ll have to have their dream election, a near perfect sweep of competitive races.

And then there’s no guarantee that all Democratic senators would go along with undoing the body’s defining characteristic.

Senators take pride in how different the Senate is from the House of Representatives. It is a chamber designed to foster collegiality and compromise and be a check on the more unruly and divisive House. So it’s probably going to take a lot of convincing for these senators to give up their power to stop an entire chamber.

Senate Democrats today are split, with strong feelings, about whether they should consider this if they win the majority next year.

“We should not be doing anything to mess with the strength of the filibuster,” Sen. Cory Booker (D-N.J.), another 2020 candidate, said in January.

“I would be shocked if the filibuster sticks around for the entirety of my second term in the Senate,” Sen. Chris Murphy (D-Conn.) told Politico in 2019, shortly after he was reelected for another six years. “It is very hard to figure out how you do a major health care reform without changing the rules.”

“Never,” said Sen. Joe Manchin III (D-W.Va.), one of the Senate’s most moderate Democrats, of voting to get rid of it.

So what Harris and Sen. Elizabeth Warren (D-Mass.) are proposing, and other 2020 candidates are considering, is a heavy lift. But it’s not impossible. Senate Democratic leaders are openly talking about considering what was once inconsiderable.

As the Hill documents, the No. 2 Senate Democrat, Sen. Richard J. Durbin (Ill.) went from “I don’t want to serve in the House again” in February to, “I tell ya, I’m reflecting on it now,” in July as Warren opened up the idea.

With enough pressure from a president, could the Senate be convinced to get rid of the filibuster? It’s possible, but still quite a long shot.