By Molly Daly

Philadelphia (CBS) — Presidential contender Mitt Romney has picked Congressman Paul Ryan of Wisconsin as his running mate. And there is reaction from New Jersey’s junior US Senator.

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As chair of the House Budget Committee, Ryan has drawn up a plan that calls for, among other measures, the privatization of Social Security, and shifts Medicare from a single-payer to a voucher-based plan.

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Senator Bob Menendez says that plan will define the Romney-Ryan campaign.

“A vision that puts the burden on the back of the middle class, and does so at the same time by giving tax breaks to the wealthiest people in the country and the wealthiest corporations in America, while snuffing out educational opportunity and healthcare security, particularly for seniors. I think that’s a dramatically stark choice from the vision that President Obama has.”

Menendez says the Obama campaign’s mission will be to make that choice clear.

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