Fifty years after President Lyndon B. Johnson declared "all-out war on human poverty and unemployment" in America, Republicans and Democrats are locked in a pitched battle over whether the United States is winning - or losing.

The debate, spilling out on Capitol Hill on the anniversary of LBJ's speech, underscores the philosophical divide between the parties and marks the open of a midterm campaign where the issue of economic inequality will take center stage.

"While this war may have been launched with the best of intentions, it's clear we're now engaged in a battle of attrition that has left more Americans in poverty than at any other point in our nation's history," Rep. Steve Southerland, R-Fla., said.

Since 1964, the government has run "the most ambitious, determined and successful campaign in history to reduce poverty since the Great Depression," Sen. Dick Durbin, D-Ill., said. "Without the public social safety net, the poverty rate in America would be nearly twice what it is today."

Both sides agree that the fight against poverty rages on, but they disagree on whether Johnson's vision of government, with expanded taxpayer-funded social benefit programs, has made sufficient inroads.

More than 46 million Americans live below the federal poverty line, which is an annual income of roughly $11,500 for an individual or $23,500 for a family of four, according to the U.S. Census Bureau. The national average unemployment rate was 7 percent at the end of 2013.

The official poverty rate, which tracks income to cover basic needs, stood at 15 percent last year, down from 19 percent in 1964, a modest decline. But a broader measure of poverty used by economists at Columbia University that accounts for noncash assistance, such as food stamps, shows a more precipitous drop since the mid-1960s, from 26 percent to 16 percent last year.

"For fifty years now, we have tried big government, yet too many people remain trapped in despair," Sen. Marco Rubio, R-Fla., said today in a highly touted address on the economy delivered in the LBJ room on Capitol Hill. "Now, we must try a new way. One that addresses the things keeping so many people from the better life they want."

Republicans, who have long favored cuts to burgeoning government benefit programs, are trying to counter Democratic attacks that they lack empathy for the poor and are callous toward the unemployed. They're trying to demonstrate heightened sensitivity to the needy, while unleashing a barrage of new economic proposals they say will significantly boost Americans' financial security and social mobility.

"When you look at the issue of poverty, there's obviously lots of facets to it," House Speaker John Boehner said today. "But the one solution that we all know that works is a job."

Meanwhile, the White House and Democrats believe they retain the upper hand, with public opinion polls showing strong support for existing social safety net programs such as Medicare, Medicaid and unemployment benefits for the long-term jobless. A measure to extend those benefits by three months hangs in the balance as Republicans insist the $6 billion cost be offset with spending cuts.

"We believe on our side of the aisle that we have to be careful in spending taxpayers' dollars, but we also believe in a safety net," Democrat Durbin said.

In a statement marking the LBJ anniversary, President Obama conceded that "far too many children are still born into poverty, far too few have a fair shot to escape it" but he said Johnson's overarching philosophy is working.

"In fact, if we hadn't declared 'unconditional war on poverty in America,'" he said, "millions more Americans would be living in poverty today. Instead, it means we must redouble our efforts to make sure our economy works for every working American."

That message is expected to be a central theme in Obama's State of the Union address later this month, when he will call for greater investment in government programs aimed at boosting the middle class, including universal preschool, infrastructure projects and job training initiatives.

"We need to provide ladders of opportunity to Americans who are in poverty, to those who are in the bottom rungs of the middle class, who are struggling to pay their bills every day, every week," White House press secretary Jay Carney said.

"You will be hearing the president talk about it again and again," he added, "as you have throughout his history in public debate."