By Dan Gilgoff, CNN.com Religion Editor

(CNN) - Roman Catholic Cardinal Timothy Dolan, America’s highest-profile Catholic official, will deliver the closing prayer at next week’s Republican convention, in another sign of how important the Catholic vote is expected to be this year.

The Archdiocese of New York confirmed Dolan’s role on Wednesday night, after it was reported by The Associated Press. News of Dolan's role initially came in an interview of presumed GOP nominee Mitt Romney by EWTN, a Catholic television network, which is scheduled to air Thursday night.

Dolan is the president of the United States Conference of Catholic Bishops, the church’s U.S. arm, and has been an outspoken critic of the Obama administration’s rule requiring insurance companies to grant employees no-cost contraception coverage.

The Catholic Church opposes contraception and wants Catholic hospitals, colleges and other institutions to be exempt from the law.

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The bishops have also been critical of the Republican budget crafted by Rep. Paul Ryan, Romney's running mate.

A spokesman for Dolan said convention protocol calls for the local bishop to deliver such a prayer, meaning the slot would have normally gone to a Florida bishop, but that the Republican convention’s organizers insisted on Dolan’s participation.

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“The Cardinal made it clear to the RNC (and to the Democratic National Committee as well) that he was only there to offer a prayer, not to engage in any partisan politics,” the spokesman, Joseph Zwilling, said in an e-mail, “and that he would be willing to accept a similar invitation from the DNC if they were to invite him to pray at their Convention as well.”

Catholics are considered the quintessential swing vote, and no presidential candidate has won the White House without winning that bloc since at least the early 1990s.

Millions of middle-of-the-road Catholic voters populate key swing states like Ohio, Pennsylvania and Florida.