Senate Republicans are considering their first filibuster of one of President Barack Obama’s executive nominees, targeting his pick to run the Department of Justice’s Office of Legal Counsel over her stances on abortion, the war on terror and potential prosecutions of Bush administration officials.

Although Indiana University law professor Dawn Johnsen’s nomination has thus far largely flown under the radar, conservatives have become increasingly vocal in their opposition to her. The Office of Legal Counsel is a particularly powerful office within DOJ, since it essentially acts as the government’s lawyers and helps provide interpretations of federal and international law.

Although Senate Judiciary ranking member Arlen Specter (R-Pa.) declined to comment on a possible filibuster until he meets with Johnsen again before leaving for recess at the end of the week, Republicans confirmed that the filibuster option has been discussed by members of the GOP Conference and that opposition to the nomination is mounting.

“My view is that the nomination should not go forward, and I think most Republicans feel the same way,— Senate Minority Whip Jon Kyl (R-Ariz.), who is a member of the Judiciary Committee, said Tuesday.

Senate Republicans said Johnsen’s nomination could provide Specter with a second chance to forcefully push back against the Obama administration.

Specter and a handful of other Senate Republicans had serious concerns with the nomination of Attorney General Eric Holder, and Specter and the GOP leadership sought to rally stiff opposition. While Republicans did not believe they could block Holder’s nomination, they had hoped to use the confirmation process to extract hard promises from the administration on a series of issues, including how Holder will approach the use of torture in the war on terror.

But a series of high-profile defections — including that of Sen. Orrin Hatch (R-Utah) — and a less-than-energetic showing by Republicans at Holder’s confirmation hearings ultimately doomed that effort, and Holder easily won confirmation.

Republicans said Tuesday that while Members have discussed the possibility of a filibuster, it remains unclear whether the GOP will decide to pull the trigger and block Johnsen on the floor.

“I don’t know if the consensus in the Conference is there to take the next step,— a veteran GOP aide said, adding that “certainly no one is comfortable with her— and that after further review, any wayward Members could be persuaded to agree to a filibuster.

Republicans said Johnsen’s record on a number of key issues has done something that has become increasingly rare in their fractured Conference — uniting social conservatives and security hard-liners.

“She’s got one of those résumés that unites the social conservatives and the war-on-terror conservatives,— a GOP leadership aide said. Johnsen has been a vocal critic of how the Bush administration conducted the war on terror and her views have rubbed hawkish conservatives in the GOP the wrong way.

Additionally, Johnsen’s stance on abortion, particularly her opposition to controls on state funding for abortions, has angered the party’s social conservatives. For instance, some 45 House Republicans, including Conference Chairman Mike Pence (Ind.), wrote Obama on March 23 urging him to pull her confirmation.

“It is important to recognize that Ms. Johnsen has no interest in reducing the number of abortions,— the lawmakers wrote, adding that the Office of Legal Counsel needs a “leader who will place the rule of law above political philosophy or personal agenda.—

A third issue that has also angered a number of old-line GOP Senators has been Johnsen’s stance on the possibility of prosecuting former Bush administration officials for their actions while in office. She has long maintained that it would be inappropriate for the Obama administration to simply decide not to pursue any potential cases against Bush officials, a stance that has won her praise from the Democratic Party’s progressive wing.

But Republicans, particularly in the Senate, have bristled at the idea of the new administration looking to pursue charges against Bush officials, maintaining it would set a dangerous precedent for “political prosecutions.—

“That’s a huge issue in our Conference … if you look at any of the hearings, that’s what the questions are about,— the leadership aide noted.

Democrats, however, rejected Republicans’ concerns as purely political and derided their efforts thus far to work up public outrage about Obama’s nominees.

“These are the same people who Karl Rove and Rush Limbaugh told to block Eric Holder. And Eric Holder got a larger vote than any of the four previous attorneys general,— Senate Judiciary Chairman Patrick Leahy (D-Vt.) said.

“These are the same people who voted unanimously for [former Bush Attorney General] Alberto Gonzales … and now they have a problem with one of Obama’s qualified nominees? I don’t think the American people will stand for it,— Leahy added.

Should Republicans ultimately decide to filibuster Johnsen’s nomination, it could be a boon to Specter’s re-election efforts. Specter is looking at a tough primary challenge from former Rep. Pat Toomey, who came within 17,000 votes of defeating him in the 2004 GOP primary. A recent poll showed Toomey with a double-digit lead over Specter in a hypothetical Republican primary, but with many voters still undecided and the primary more than one year away.

Specter also faces a dwindling base across the state as hundreds of thousands of moderate Republicans have changed their registrations to Democratic since 2004 in the Keystone State. Specter is at a disadvantage in the closed GOP primary without those moderate Republicans and will likely have to mount a voter registration drive to switch some of those Democrats back before 2010.

But a filibuster of Johnsen could help Specter significantly bolster his conservative credentials with the voters back home. One Republican said a filibuster “could be very good for him,— particularly because opposition to Johnsen’s nomination runs the spectrum of conservative constituencies.

But even if Specter survives the GOP primary, the general election promises to be another tough contest for the moderate Republican. Pennsylvania has voted increasingly for Democrats since his last election, ousting conservative Republican Sen. Rick Santorum in 2006 and losing five GOP House Members since 2004.

Former National Constitution Center President Joe Torsella has announced he is running for the Democratic nomination, but he mostly likely won’t be the only Democrat to run statewide.

Shira Toeplitz contributed to this report.