When 12 religious leaders in collars and vestments were arrested last week in the atrium of the Hart Senate Office Building in Washington, they were reading Bible verses about caring for the poor, and doing it so loudly that their voices could be heard at the doors of senators’ office suites nine stories above.

It was to little avail: The Senate went ahead and passed a tax bill early on Saturday, promoted as relief for the middle class, that mainly benefits corporations and the rich — and that many economists say offers little or nothing for the poor.

The middle class and its discontents have occupied so much political and media attention lately that poverty has been crowded out. But some prominent religious leaders are gearing up for a campaign to try to put it back on the nation’s agenda in a way that it hasn’t been in decades.

On Monday, exactly 50 years after the Rev. Dr. Martin Luther King Jr. began his Poor People’s Campaign, the Rev. Dr. William J. Barber II, a black minister and civil rights leader from North Carolina, and the Rev. Dr. Liz Theoharis, a white theologian originally from Milwaukee, will announce a revival of Dr. King’s campaign, which stalled when he was assassinated in 1968. Organizers now hope to mount large protests on 40 consecutive days next year, in at least 25 state capitals and other locations, with crowds in the tens of thousands courting arrest.