Sen. Jeff Sessions, R-AL, an ardent conservative, is all but certain to assume the top GOP spot on the Judiciary Committee replacing Sen. Arlen Specter of Pennsylvania, who last week switched parties, FOX News has learned.

One GOP aide said Sessions was chosen as Ranking Republican after member-to-member conversations over the weekend, but Judiciary Committee Republicans are expected to meet Monday evening to formally select their top GOPer.

This is all but certain to mean a difficult fight over the replacement of Supreme Court Justice David Souter.

Sessions, according to GOP sources, is expected to serve out the remainder of the session, which ends in Jan, 2011, after which seniority could see a change in ranking positions on several top committees. Grassley is in line to take over the Judiciary Committee; Sessions moving to the Budget Committee; and Hatch, a senior Judiciary Committee Republican, is in line to head the Finance Cmte. Republicans, unlike Democrats, base their top spots on seniority, but one senior GOP leadership aide said, "Anything can happen. Sessions can decide to stay on Judiciary, then that opens up a problem."

Interestingly, it was the Judiciary Committee which, back in 1986, rejected Sessions for a judgeship. Sessions was then the U.S. attorney for the Southern District of Alabama. President Reagan nominated him (in 1985) to be a district judge, but two Republicans, one being Arlen Specter (!!), joined all committee Democrats to defeat the nomination 10-8.

rights groups at the time objected to Sessions because of some statements he had made about race in voter fraud cases.

He has a pro-life voting record; is a vocal opponent of comprehensive immigration reform; and has voted to bar same sex marriage.