WASHINGTON — The election-year fight over the administration’s birth control policy escalated Friday, with two unlikely figures — a Georgetown University law student and the conservative radio host Rush Limbaugh — taking center stage in the politically charged conflict and pulling much of official Washington into the fray.

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On Friday, one day after Senate Democrats beat back a Republican challenge to the new policy, President Obama called Sandra Fluke, the Georgetown student who had come under incendiary attack from Mr. Limbaugh, to thank her for publicly backing his regulations mandating contraception coverage.

The call by Mr. Obama to Ms. Fluke, an activist on the issue who had been barred by Republicans from testifying at a House hearing last month, provided new fuel to a dispute that has already spilled over into Congress and onto the campaign trail and was becoming a major source of contention between the two parties. Republicans have tried to use the issue to rally conservatives and Catholic voters who see the contraceptive mandate as an infringement on religious liberty.

But in Ms. Fluke and the scorn she has drawn from conservative commentators, Democrats may have found a symbol for what they have called a Republican “war on women” that could spell more difficulty for a Republican Party already showing signs of trouble with female voters.

The White House press secretary, Jay Carney, said the president told Ms. Fluke that he stood by her in the face of personal attacks on right-wing radio. Mr. Obama believes, Mr. Carney said, that Mr. Limbaugh’s comments about Ms. Fluke were “unfortunate attacks,” and Mr. Carney called them “reprehensible.”

Ms. Fluke, 30, also drew support from the president of Georgetown University, who has differed with her in the past over the university’s refusal to provide insurance coverage for contraception.

The university president, John J. DeGioia, said in a statement: “One need not agree with her substantive position to support her right to respectful free expression. And yet, some of those who disagreed with her position — including Rush Limbaugh and commentators throughout the blogosphere and in various other media channels — responded with behavior that can only be described as misogynistic, vitriolic, and a misrepresentation of the position of our student.”

Mr. Obama phoned her just before she was to appear on MSNBC.

“He encouraged me and supported me and thanked me for speaking out about the concerns of American women,” she told the program’s host, Andrea Mitchell. “And what was really personal for me was that he said to tell my parents that they should be proud. And that meant a lot, because Rush Limbaugh questioned whether or not my family would be proud of me.”

The tempest began after Ms. Fluke took public her campaign for contraceptive coverage at Georgetown, a Jesuit university in Washington, as Republicans and Catholic Church leaders were denouncing the Obama administration’s contraception mandate. Mr. Limbaugh subsequently called her a “slut” and a “prostitute,” drawing condemnation from Democrats.

On Friday, the House speaker, John A. Boehner, called the Limbaugh comments “inappropriate.” Rick Santorum, the former senator whose run for the Republican presidential nomination has thrust social conservatism into the spotlight, told CNN that Mr. Limbaugh was “being absurd.”

But, he added, “an entertainer can be absurd.”

In his radio show on Friday, Mr. Limbaugh said Ms. Fluke was being used as a political pawn by Democrats for fund-raising and other purposes.

“The Democrats are desperate,” Mr. Limbaugh said. “This is all they’ve got, is to go out and try to discredit their critics, to impugn and discredit the people who disagree with them.”

Democratic groups were trying to capitalize on the fight, circulating calls for support for Ms. Fluke tied to fund-raising appeals.

“Personal attacks on a student — and all women — simply can’t be ignored,” said one appeal from the Democratic Senatorial Campaign Committee. “Stand with us, and denounce Rush Limbaugh’s vile attacks.”

Ms. Fluke, a third-year law student, was no neophyte to the cause. She served as president and secretary of Georgetown Law Students for Reproductive Justice, as vice president of the Women’s Legal Alliance, and as an editor on The Georgetown Journal of Gender and the Law. In those capacities, Ms. Fluke, a Cornell graduate, had other run-ins with the university over contraception access.

A week after she was shut out of the House hearing, House Democrats gave her a platform at an informal Democratic event where she testified that fellow students at her Jesuit university pay as much as $1,000 a year for contraceptives that are not covered by student health plans.

On his Wednesday show, Mr. Limbaugh said: “What does that make her? It makes her a slut, right? It makes her a prostitute.” Those remarks and others whipped up a frenzy of denunciations, but on Thursday, Mr. Limbaugh held his ground, declaring: “If we’re going to pay for your contraceptives and thus pay for you to have sex, we want something for it. We want you to post the videos online so we can all watch.”

Mr. Boehner condemned those comments Friday, but also denounced Democratic fund-raising efforts stemming from the latest Limbaugh imbroglio.

“The speaker obviously believes the use of those words was inappropriate, as is trying to raise money off the situation,” said a Boehner spokesman, Michael Steel.

Some advertisers also expressed concern. On Friday, as complaints about Mr. Limbaugh’s comments mounted, a handful of companies said that they had halted their advertising on “The Rush Limbaugh Show,” at least temporarily. One of the companies, Quicken Loans, wrote on Twitter, “Due to continued inflammatory comments — along with valuable feedback from clients and team members — QL has suspended ads on Rush Limbaugh program.”

On Thursday, Representative Nancy Pelosi of California, the House minority leader, said in a fund-raising appeal that the Democratic Congressional Campaign Committee’s “women’s health rapid response fund” had raised $1.1 million and was nearing 500,000 signatures “on our petition against Republicans’ disgraceful assault on women’s rights.”

By Friday afternoon, the campaign committee had raised $1.6 million since Feb. 24, the day after Representative Darrell Issa’s hearings on the issue. Two petition drives had netted 600,000 signatures; 152,000 signed the Democratic petition on Thursday alone.

Republicans condemned such efforts, but the National Republican Congressional Committee launched its own fund-raising campaign against what it called “the Obama administration’s decision to trample on the religious liberty of Christian charities — forcing them to provide free birth control.”