Ryan has argued that his budget plan is informed by Catholic social teaching and that reducing the federal deficit through budget cuts would help the poor and all Americans by allowing the economy to grow.
The bishops, with some notable exceptions, have countered that Ryan's budget violates Catholic social teaching by emphasizing cuts in programs for the needy while reducing taxes for the wealthy. Ryan's plan has also been criticized as likely to expand rather than reduce the national debt.
By framing her critique in the context of her Christian faith, Campbell was using the kind of religious language that has been a hallmark of the GOP's campaign to rally believers behind Romney and Ryan.
But she also sought to identify the sisters and the Democratic agenda with Catholic tradition at a time when Catholic voters who comprise close to a quarter of the electorate are considered key to November's election.
Just as important, Campbell neatly folded her remarks in with statements from the Catholic hierarchy, which has had more than its share of disagreements with President Barack Obama and the Democratic Party over issues like gay marriage and abortion.
"We agree with our bishops, and that's why we went on the road: to stand with struggling families and to lift up our Catholic sisters who serve them," said Campbell, who heads a Washington-based Catholic social justice lobby called Network. "Their work to alleviate suffering would be seriously harmed by the Romney-Ryan budget."
In her seven-minute speech, Campbell did not address hot-button issues such as abortion directly, but she earned the loudest ovation when she defended Obama's health care reform law as a cause she considers "part of my pro-life stance and the right thing to do."
Like many other speakers at the convention in Charlotte, N.C., Campbell framed the election as a choice between a philosophy of individualism championed by Republicans and a more communitarian approach to society building emphasized by Democrats.
She also underscored the plight of poor and working-class Americans in the recession, and pointed to Democratic policies as both the most effective answer and the most moral one.
"During our journey, I rediscovered a few truths," Campbell said. "First, Mitt Romney and Paul Ryan are correct when they say that each individual should be responsible. But their budget goes astray in not acknowledging that we are responsible not only for ourselves and our immediate families. Rather, our faith strongly affirms that we are all responsible for one another."
"I am my sister's keeper. I am my brother's keeper," she said to applause.