President Joe Biden will lay out the “moral case” for voting rights as he faces growing pressure from civil rights activists and other Democrats to combat efforts by Republican-led state legislatures to restrict access to the ballot.

Biden has declared that protecting voting rights was the central cause of his presidency, but the White House has taken sharp criticism from allies for not doing more while contending with political headwinds and stubborn Senate math that have greatly restricted its ability to act.

Biden’s speech on Tuesday in Philadelphia, to be delivered at the National Constitution Center, is intended as the opening salvo of a public pressure campaign, White House aides said, even as legislative options to block voting restrictions face significant obstacles.

“He’ll lay out the moral case for why denying the right to vote is a form of suppression and a form of silencing,” White House press secretary Jen Psaki said Monday as she previewed the speech.

“He will redouble his commitment to using every tool at his disposal to continue to fight to protect the fundamental right of Americans to vote against the onslaught of voter suppression laws.”

Several states have enacted voting restrictions, and others are debating them, as Republicans have seized on former President Donald Trump’s false claim of massive voter fraud in the 2020 election as a pretense for curtailing ballot access.

Psaki said on Monday that Biden will vow to “overcome the worst challenge to our democracy since the Civil War.” But aides have suggested that his address will not contain much in the way of new proposals.

Moderate Democrats like Sen. Joe Manchin of West Virginia and Sen. Kyrsten Sinema of Arizona so far have expressed reluctance to changing the Senate tradition.

Biden’s long-awaited speech was to roll out just hours after a group of Democratic Texas lawmakers arrived in the nation’s capital after fleeing their state to try to kill a Republican bill making it harder to vote in Texas.

The legislators said they were ready to remain in Washington for weeks, forcing a dramatic new showdown over voting rights in America.

Private planes carried a large group of Democrats from Austin to Washington, the lawmakers skipping town just days before the Texas House had been expected to give early approval to sweeping new voting restrictions in a special legislative session.

They hoped to deprive the Legislature of a quorum – the minimum number of representatives who have to be present for the body to operate.

“Our backs are against the wall. This is the moment. We have no more time,” said Sherrilyn Ifill, president of the NAACP Legal Defense Fund, after the meeting.