Ending weeks of internal debate, Senate Republican leaders have decided to file cloture on the stalled judicial nomination of Miguel Estrada, setting up the first in a series of votes Thursday in their effort to break the Democratic filibuster.

Aides said the full Republican Conference was expected to sign off on the strategy at its weekly policy luncheon Tuesday unless there was a “dramatic reversal” in the tide of opinion.

Another Republican source, however, cautioned that there was a large contingent within the Conference opposed to filling cloture, a bloc that could provide that dramatic sway and reverse the movement toward cloture.

Emerging from a meeting of GOP chairmen and leaders Monday night, Conference Chairman Rick Santorum (Pa.) declined to specify what decisions had been made, but indicated that an announcement of their strategy was expected after the luncheon.

One GOP aide indicated that the new tactic calls for Majority Leader Bill Frist (R-Tenn.) to file cloture Tuesday afternoon, leading to the Thursday vote. The aide said there is no expectation of winning the 60 votes needed to break the filibuster, but that Frist would continue to force “as many cloture votes as is necessary to win confirmation.”

“They’ll be frequent and they’ll be prominent,” the aide said.

With 45 Democrats dug in on their opposition to Estrada, Republicans had been divided over how to proceed with the battle over President Bush’s nominee to the U.S. Court of Appeals for the D.C. Circuit.

Santorum and Majority Whip Mitch McConnell (R-Ky.) had been the leading opponents of filing cloture, warning that it would set a bad institutional precedent of requiring 60 votes for nominees and could doom Estrada’s hopes for confirmation by locking in Democrats in conservative-leaning states.

But others, including Sen. Trent Lott (R-Miss.) and Judiciary Chairman Orrin Hatch (R-Utah), had been pushing for cloture, arguing that putting Democrats officially on the record in support of the filibuster would allow outside conservative interest groups to heighten the pressure on them.

The Democrats’ top vote counter, Minority Whip Harry Reid (Nev.), said there may be a couple of Democrats who are wavering on Estrada, but there was no doubt he had the minimum of 41 votes needed to block a vote, no matter how many cloture votes Republicans call.

“We have 41, that’s all we care about,” Reid said.

So far, Democratic Sens. John Breaux (La.), Zell Miller (Ga.), Ben Nelson (Neb.) and Bill Nelson (Fla.) have announced their support for Estrada.