In an unsparing critique of Republicans, President Barack Obama on Friday said the GOP is threatening voting rights in America more than at any point since the passage of the historic 1965 law expanding rights at the ballot box to millions of black Americans and other minorities.

“The stark, simple truth is this: The right to vote is threatened today in a way that it has not been since the Voting Rights Act became law nearly five decades ago,” Obama said in a fiery speech at civil rights activist and television talk show host Al Sharpton’s National Action Network conference.

The election-year warning comes as Obama seeks to mobilize Democratic voters to fight back against state voting requirements and early balloting restrictions that many in his party fear will curb turnout in November.

Obama’s speech came a day after he marked the 50th anniversary of the Civil Rights Act at the LBJ Library in Austin, Texas, where he praised President Lyndon Johnson’s understanding of presidential power and his use of it to create new opportunities for millions of Americans.

The president pinned efforts to curb access to the ballot box directly on the GOP, declaring that the effort “has not been led by both parties. It’s been led by the Republican Party.”

No political issue stands out more prominently for Democrats than their ability to motivate voters to turn out at the polls in November. Control of the Senate, now in the hands of Democrats, is at stake, as is Obama’s already limited ability to push his agenda through Congress.

Republicans have long argued that identification requirements and other voting controls are reasonable measures designed to safeguard the balloting process. Democrats say photo identification requirements especially affect minority or low-income voters who might not drive and wouldn’t have a government ID.

“I want to be clear: I am not against reasonable attempts to secure the ballot. We understand that there have to be rules in place,” Obama said. “But I am against requiring an ID that millions of Americans don’t have. “

Seven states passed voter restrictions last year that range from reductions in early voting periods to ID requirements, according to the Brennan Center for Justice at New York University School of Law. North Carolina adopted a photo ID requirement, eliminated registrations on Election Day and reduced the number of early voting days. Overall, 34 states have passed laws requiring voters to show some form of identification at the polls.

The North Carolina steps, which take effect in the 2016 election, came after the Supreme Court last June threw out the section of the Voting Rights Act requiring that all or parts of 15 states with a history of discrimination in voting get federal approval before changing their election laws.

Bipartisan legislation proposed in the House and Senate would attempt to address the constitutional concerns raised by the Supreme Court.

The proposed bill would require four states — Georgia, Louisiana, Mississippi and Texas —to get approval from the Justice Department before making any changes in the way they hold elections. In an effort to secure Republican votes, it provides an exception for states that want to adopt photo identification requirements.

Offering a potential compromise, former U.N. Ambassador Andrew Young, once a top aide to the Rev. Martin Luther King Jr., suggested this week that Obama use his executive power to require optional photos on Social Security cards as a remedy for states that impose voter ID laws.

Meanwhile, the administration is stepping up its offensive. Attorney General Eric Holder has challenged the North Carolina election law as well as one in Texas.