“This battle is not over,” President Biden vowed at South Carolina State University.

He was not speaking about his Build Back Better bill, the $2 trillion spending measure that’s been blocked by Sen. Joe Manchin, the West Virginia Democrat who holds veto power over the president’s legislative agenda. Rather, Biden’s promise refers to two critical proposals that would restore and protect fundamental rights: to vote freely and to have your ballot counted fairly.

Build Back Better is a wish list of liberal aspirations, from expanding child tax credits to offering incentives for green energy options. None of those measures, however worthy, are absolutely essential to a healthy functioning democracy.

Protecting voting rights, however, is essential. Without fair elections, the whole system fails. As Sen. John Hickenlooper of Colorado told Dan Balz of the Washington Post: “Voter disenfranchisement threatens our entire democracy … all your other rights are dependent on your right to vote.”

Biden’s words are especially urgent because Republicans are conducting a deliberate and destructive campaign to undermine voting rights. As the Brennan Center for Justice reports, “In an unprecedented year so far for voting legislation, 19 states have enacted 33 laws that will make it harder for Americans to vote.”

“I’ve never seen anything like the unrelenting assault on the right to vote,” Biden thundered at South Carolina State. “Never.”

That assault is particularly pernicious because it’s based entirely on a Big Lie: that the presidency was stolen from Donald Trump and future elections are jeopardized by voter fraud. It cannot be said often or clearly enough: THAT IS NOT TRUE. Countless Republican officials — governors, election monitors, federal judges appointed by Trump, even his own attorney general, Bill Barr — all agree that the election was honest, that fraud was minimal and that Biden won fairly and squarely.

There is simply no explanation — none — for the new laws, except for one: Republicans want to suppress Democratic votes and make it easier for themselves to win. It’s now Democrats who should be shouting “Stop the steal!”

Here’s the problem, however: Democrats have only 50 votes in the Senate, but they need 60 to overcome Republican filibusters, and the GOP has repeatedly stonewalled all attempts to bring the voting rights reforms to the floor. And so far Manchin, with the support of Arizona Sen. Kyrsten Sinema, has refused to consider changes in the filibuster rules that would free the voting bills from limbo.

Now, Manchin makes a good point: Changes in Senate rules are best done through bipartisan consensus, otherwise the basic culture of the chamber is threatened with chaos. Sinema adds, correctly, that if Democrats abrogate the filibuster to pass voting rights, a Republican majority could easily roll back those changes in the future and pass even more draconian voting restrictions.

Indeed, Democrats have already seen the risks of tampering with the rules. In 2013, they amended the filibuster so it could not be used to shelve President Obama’s picks for federal judgeships. So, four years later, Republicans felt free to end the filibuster for Supreme Court nominees. Do you think Democrats regret not having the leverage to stop Trump’s choice of Justice Amy Coney Barrett in the last months of his presidency? You betcha.

But politics always involves a balancing of costs and benefits. And since Republicans have changed the basic ground rules, the potential rewards of altering the filibuster now outweigh the risks.

The odds are stacked heavily against the Democrats, but there are a few flashes of hope. For one thing, while Manchin denounced the substantive provisions of Build Back Better, he actually supports voting rights reforms. Sinema, too, says she favors the measures; she just opposes the process needed to pass them.

The filibuster rule is hardly immutable, however. It has been changed more than 160 times. Key measures like budgets, trade bills and even military base-closing proposals are exempt from the filibuster. Just recently, the Senate again abrogated the rule to allow an increase in the national debt ceiling.

The Senate leader, Chuck Schumer, has vowed to press the issue of voting rights early in the new year and “consider changes to any rules which prevent us from debating and reaching final conclusion on important legislation.”

Manchin, Sinema and other moderate Democrats — including Biden himself — have rightly been reluctant to weaken the filibuster and possibly shred the remnants of Senate civility. But the Republican attack on voting rights really does threaten our entire democracy. And that threat has to be thwarted by a decisive response.

(Steven Roberts teaches politics and journalism at George Washington University. He can be contacted by email at stevecokie@gmail.com.)