WASHINGTON (AP) _ In an election-year pitch to middle-class voters, President Barack Obama is denouncing a House Republican budget plan as a “Trojan horse,” warning that it represents “an attempt to impose a radical vision on our country” that would hurt the pocketbooks of working families.

Obama, in a speech to newspaper executives, is sharply criticizing a $3.5 trillion budget proposal pushed by Rep. Paul Ryan, R-Wis., which passed on a near-party-line vote last week and has been embraced by GOP presidential hopefuls. The plan has faced fierce resistance from Democrats, who say it would gut Medicare, slash taxes for the wealthy and lead to deep cuts to crucial programs such as aid to college students and highway and rail projects. “It’s a Trojan horse. Disguised as deficit reduction plan, it’s really an attempt to impose a radical vision on our country,” Obama said in excerpts of his speech released Tuesday. “It’s nothing but thinly veiled social Darwinism.”

Obama’s message comes as Republican Mitt Romney looked to solidify his grip on his party’s presidential nomination in primary contests in Wisconsin, Maryland and Washington, D.C. The White House has appeared increasingly focused on Romney, with Obama’s campaign criticizing the former Massachusetts governor by name in an energy ad as the president’s team seeks to frame the election as a referendum on the economic security of middle-class voters.

White House advisers billed the speech _ to be delivered during The Associated Press luncheon of editors and publishers _ as an important marker for the president as he seeks re-election. Senior administration officials said the address would build upon themes the president delivered in Kansas last fall, in which he called the nation’s economic challenges a “make-or-break moment” for the middle class, and in his State of the Union address, in which he laid out his election-year agenda.

Ryan’s proposal aims to slash the deficit and the size of government while offering sharply lower tax rates in return for eliminating many popular tax breaks. GOP front-runner Mitt Romney and his Republican rivals have said they would support Ryan’s budget plan, which has little chance of passing the Democratic-controlled Senate but lays out the GOP’s fiscal priorities.

Obama was making the case that whoever wins the White House will face an economy still recovering from the “worst economic calamity since the Great Depression” and many Americans will still be looking for jobs and lacking financial security. By next year, “a debt that has grown over the last decade, primarily as a result of two wars, two massive tax cuts and an unprecedented financial crisis, will have to be paid down,” Obama says in the prepared remarks.

He argues that Ryan’s budget plan would stall the economic recovery. “By gutting the very things we need to grow an economy that’s built to last _ education and training, research and development _ it’s a prescription for decline,” he says.

On taxes, Obama is also expected to call for economic fairness encapsulated by the so-called “Buffett Rule,” arguing that the wealthy shouldn’t pay a smaller share of their income in federal taxes than middle-class taxpayers. Many wealthy taxpayers earn investment income, which is taxed at 15 percent, and Obama has proposed that people earning at least $1 million annually, whether in salary or investments, should pay at least 30 percent of their income in taxes.

Obama planned to note that “broad-based prosperity has never trickled-down from the success of a wealthy few. It has always come from the success of a strong and growing middle class.”

The focus on tax reform has brought attention to the effective tax rate of Romney, a millionaire who is paying 15.4 percent in federal taxes for 2011 on income mostly derived from investments. The top nominal rate for taxpayers with high incomes derived from wages, not including investments, is 35 percent.

In advance of Obama’s speech, political adviser David Axelrod charged that Romney is “just in a time warp,” saying the former Massachusetts governor “seems to look at the world through the rear-view mirror.” He said Romney subscribes to a Cold War-era belief that Russia is America’s greatest foe in the world and would return the country to outmoded economic policies that led to the near economic meltdown in the fall of 2008.

“I think he must watch Madmen and think it’s the evening news,” Axelrod said in an appearance on “CBS This Morning.” He said that Romney “wants to go back to the same policies that got us into this disaster.”

Obama was speaking at a luncheon of 900 editors and publishers following The Associated Press’ annual meeting. William Dean Singleton, outgoing chairman of the AP Board of Directors and chairman of MediaNews Group Inc., will pose questions to Obama following the president’s remarks.