The late Senator Lindsey Graham has been betrayed... by his own sister. Darline is abandoning his cause: DAN MCLAUGHLIN

Darline Graham just trashed her brother's Senate legacy.

Lindsey must be rolling over in his grave.

When Lindsey Graham died on July 11, President Donald Trump recommended that his seat be filled by his sister Darline, the senator's next of kin.

South Carolina Governor Henry McMaster dutifully appointed her to serve out the remaining six months of Lindsey's term. Now, a special election is underway to select an official Republican nominee to run in November.

I've always felt that there was something distasteful about handing down Senate seats as if they were family heirlooms, but under the circumstances, the appointment seemed to make sense.

A close family member like Darline would presumably know Lindsey's thinking well enough to ensure that she votes the same way he would have, thus giving voters the type of representative they had originally selected.

Installing a family member who knows the departed senator's team also makes it more likely that trusted staffers remain in place, avoiding the burden of training new people for a very short tenure.

Lastly, a political amateur like Darline Graham, 62, who's never held office before, would presumably act as a placeholder while more experienced candidates ran to occupy the seat for the full term.

But that's not happening here.

Darline plans on staying.

She's running in the primary and if Monday night's South Carolina Republican debate is any indication, she's playing for keeps, vowing to do something her brother opposed: eliminate the filibuster to pass one of President Trump's preferred pieces of legislation: the Save America Act.

The bill would, among other measures, require voter ID and proof of citizenship for voter registration nationwide. It does some worthwhile things, although I am skeptical of having a federal law override the states in this area. Graham supported the SAVE America Act, but not by any means necessary.

The filibuster has long been treasured as an institutional safeguard against controversial legislation, even if it has the support of a majority of senators, from becoming law.

This political tool requires a three-fifths majority of the Senate (60 out of 100 senators) from at least 30 states to vote to end debate on a bill and send it to the floor for a final up-or-down vote.

Simple majority rule doesn't cut it in the Senate. That's how the House operates, but in the Senate – the world's greatest deliberative body – members are expected to reach an overwhelming consensus.

This guarantees that Americans from all regions and walks of life have an opportunity to have their voices heard before new national law is created.

'The pride of the Senate,' Lindsey Graham said in 2022, 'is that to pass bills, you've got to get some buy-in from the other side to keep wild shifts from happening in American politics.'

Indeed, the filibuster may have stopped a lot of bad ideas, but it hasn't always been used wisely.

Southern Democrats, for instance, relied on the filibuster in the 1950s and 1960s to block civil rights bills. The longest one-man filibuster in Senate history was by South Carolina's Strom Thurmond, who single-handedly held the floor for over 24 hours to block the Civil Rights Act of 1957. Thurmond was succeeded in his Senate seat in 2003 by Lindsey Graham.

In 1975, after Democrats scored 62 votes in the Senate, they dropped the cloture threshold from two-thirds to 60. Today, many Democrats want to end the filibuster altogether if and when they return to power.

Only the opposition of two Democrats (plus every Republican) held the filibuster in place during Joe Biden's presidency. Those Democrats, Kyrsten Sinema and Joe Manchin, were then hounded out of their party. But their votes prevented Biden from passing a battery of laws that Democrats supported, including a national voting bill that would have outlawed voter ID.

Historically, it has been progressives and liberals who have lamented the filibuster as an unnecessary obstacle to their designs. But Republicans have been willing to retaliate when Democrats break the system.

Longtime leader Mitch McConnell argued for decades that the filibuster prevents more bad progressive laws than good conservative ones. After Democrats abolished the filibuster for appeals-court judges in 2013, he warned that they would regret it sooner than they expected. In April 2017, McConnell retaliated by eliminating the filibuster for Supreme Court nominees, allowing confirmation by a simple majority. McConnell believed in the judicial filibuster, but once it was half-broken, he finished it off.

In the face of Democratic obstructionism, McConnell was arguably justified, but the move undeniably undermined the filibuster's institutional strength.

Lindsey Graham, as a longtime McConnell ally, was vocal in opposing schemes by either party to change the rules regarding filibusters.

During Trump's first term, Graham co-signed a letter with some Senate Democrats pledging to maintain the filibuster; in 2022, he called on those Democrats to keep their promise: 'I am asking no more of them than I asked of myself and my colleagues when we were in a similar position.'

Maybe the Democrats will have the votes sometime soon to end the filibuster. But if they do, they should have to pay the political price for their radicalism – not have it paid for them by Republicans.

When Democrats ended the filibuster for appeals-court judges in 2013, they lost nine Senate seats, and they've reclaimed just one since then.

Darline Graham, however, has agreed to do Trump's bidding. 'This is where I differ from my brother,' she said on Monday, 'getting rid of the filibuster to get this done. Because eventually the Democrats are going to get rid of it anyway.'

She might be correct. But that doesn't make what she's doing right.

Early polling shows Darline Graham leading the general election race in November, but in a divided five-way field.

It would be tragic if she won an election but destroyed her brother's legacy in the process.