(Image Credit: Pablo Martinez Monsivais/AP Photo)

President Obama today will accuse his Republican rivals of supporting a budget that is nothing more than a "Trojan Horse," as he continues to cast himself as a defender of the middle class.

"Disguised as [a] deficit-reduction plan, it's really an attempt to impose a radical vision on our country.  It's nothing but thinly veiled Social Darwinism," the president will say at the Associated Press luncheon today, according to prepared remarks.

The president will harshly criticize the $3.5 trillion budget proposed by Rep. Paul Ryan, R-Wis., which has been supported by the Republican presidential candidates. The plan has come under attack from Democrats who claim it supports the interests of the super-wealthy and would gut Medicare.

"It's antithetical to our entire history as a land of opportunity and upward mobility for everyone who's willing to work for it. a place where prosperity doesn't trickle down from the top, but grows outward from the heart of the middle class," the president will say. "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."

The president is expected to argue that the nation is at a make-or-break moment for the middle class and to continue to push his proposed Buffett Rule, which would require people earning $1 million a year to pay at least the same tax rate as middle-class families.