MESA, Ariz.—Republicans Mitt Romney and Rick Santorum are sparring in what is likely to be the final debate before the next slate of states has nominating contests, trading barbs on Washington spending and borrowing.

Romney on Wednesday said government doubled in size while Santorum served in the House and Senate. Romney notes that Santorum voted to increase the nation's borrowing limit five times without corresponding budget cuts, as well as voting to send tax dollars to Planned Parenthood.

By contrast, Romney says he balanced budgets during his four years as Massachusetts governor and at the helm of the Olympic Games.

Santorum is not letting Romney have a pass on it. He says that Romney supported last year's vote to increase the nation's borrowing limit to avoid a government default.

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