A Quinnipiac poll released Wednesday showed Biden’s approval rating at 33%, the lowest of his presidency.

Biden and Senate Democrats had begun the new year with plans to quickly advance the voting rights bill, after Democratic Senator Joe Manchin rejected the president’s economic agenda. Yet the sudden push on voting rights, highlighted in a speech by Biden in Atlanta on Tuesday, was quickly panned by civil-rights groups that accused the president of doing too little, too late on a vital issue for Black voters.

The challenge for Biden on voting rights deepened Thursday. Hours before Biden was to sell his plan in a closed-door meeting with Senate Democrats, Senator Kyrsten Sinema of Arizona rejected White House-backed efforts to change Senate rules to win approval of the legislation, uniformly opposed by Republicans.

Her opposition — outlined in a speech from the Senate floor — deprived Biden of crucial support in a chamber divided 50-50. Republicans oppose the voting rights measures.

Biden said if the measure fails in the Senate, he’ll try again.

“As long as I have a breath in me, as long as I’m in the White House, as long as I’m engaged at all, I’m going to be fighting” for legislation to counter measures in Republican-led states that limit voting rights, he said.

He met with Manchin and Sinema on Thursday night for a little over an hour to discuss voting rights, a White House official said, without giving details.

‘Broader Challenges’

Sinema said her support for the filibuster, which requires 60 votes for most legislation to advance, protects the country “from wild reversals on federal policy” when control of Congress changes hands.

“While I continue to support these bills, I will not support separate actions that worsen the underlying disease of division infecting our country,” Sinema said.

Manchin in a statement issued later in the day also reaffirmed his commitment to keeping the filibuster intact.

“Allowing one party to exert complete control in the Senate with only a simple majority will only pour fuel onto the fire of political whiplash and dysfunction that is tearing this nation apart – especially when one party controls both Congress and the White House,” he said.

At issue is the fate of two voting rights measures that were combined into a single bill passed by the House earlier Thursday. Senate Majority Leader Chuck Schumer has set up the legislation as a test of the Senate rules that give the minority party broad power over what bills can get a vote.

QuickTake: Why the Filibuster Is Target for Impatient Democrats

To overcome a Republican blockade, Biden has sought to persuade Sinema and Manchin to go along with altering the filibuster to get the legislation passed.

Difficult Path

Maine Senator Angus King, an independent who caucuses with Democrats, said Sinema’s remarks made the path forward “very difficult.”

“She believes that the risk of changing the filibuster is greater than the risk of what’s going on in the states,” he said. “I hope profoundly that she’s right. I fear that she’s wrong.”

Republicans, who have blocked voting legislation in the past, praised Sinema for opposing changing the Senate rules.

“It was extraordinarily important,” Senate GOP leader Mitch McConnell said. “And she has, with a conspicuous act of political courage, saved the Senate as an institution.”

During his private meeting with senators, Biden said the U.S. is facing a “systematic effort to dismantle democracy” and that passing the legislation is a “historic chance to save our democracy,” according White House Press Secretary Jen Psaki. But his remarks didn’t appear to sway lawmakers standing in the way of passage.

Earlier: Biden Takes Up Voting Rights as His Allies Fret, GOP Digs In

Schumer said after Biden left that Democrats would do everything they can to pass the voting rights legislation, but he didn’t set out a plan.

As part of a procedural gambit, the House earlier Thursday put the two elections measures into an unrelated NASA bill that had already passed the Senate. That will allow Schumer to bring the bill up for debate without risk of a Republican filibuster, but it still will need 60 votes to move to a vote on final passage.

At that point, Schumer had planned to seek a Senate rules change by a simple majority vote. But that requires agreement from all Democrats and the Senate’s two independents.

Manchin and Sinema aren’t alone in their wariness of significantly changing the filibuster rules. Others, including Jon Tester of Montana, say they don’t want to have a one-time “carve out” to end the filibuster simply to pass the voting rights legislation.

Underscoring the tenuous position Democrats are in, Senator Brian Schatz of Hawaii said he tested positive for Covid-19 earlier this week and was isolating at home. It was unclear how soon he would return, and his vote is likely needed to begin debate on the bill or to change Senate rules.

–With assistance from Justin Sink.