As Senate Democrats struggle to hammer out a compromise bill on union organizing, Majority Leader Harry Reid (D-Nev.) is sketching a process for railroading the bill through the floor as quickly as possible to prevent Republicans from rallying a major campaign against it, senior Democratic aides said.

Talks on the bill are ongoing, and with health care on the Senate’s plate, Democrats said no deal on the labor bill is expected until September at the earliest — if at all.

Sen. Tom Harkin (D-Iowa) has been working for months to put together a deal on “card check— legislation, which would make it easier for workers to unionize. Democrats had originally hoped to move a bill that would include not only that language changing how workers vote to join a union but also a provision requiring workers and employers to submit to binding federal arbitration to settle labor disagreements.

Business groups and Republicans have spent more than a year — and tens of millions of dollars — attacking the proposed Employee Free Choice Act, and by this spring, Harkin had lost not only the handful of Republicans that had supported similar bills but also a number of moderate Democrats. The bill essentially stalled in March, when then-Republican Sen. Arlen Specter (Pa.) announced he would oppose it. Specter has since switched parties.

Since that time, Harkin and a small group of Democrats — including Arkansas Sens. Mark Pryor and Blanche Lincoln — have held on-again, off-again negotiations in an effort to restart the legislation, including the possibility of moving the arbitration provisions alone.

Despite news reports earlier this month that a deal had been cut, negotiations are continuing. “There’s no bill yet,— Lincoln said late last week.

As Harkin tries to build a consensus Democratic bill, Reid has been thinking through a strategy to pass it that would require not only the support of all 60 Democrats in the Senate, but also the physical presence of ailing Sens. Edward Kennedy (D-Mass.) and Robert Byrd (D-W.Va.) for floor votes, since Republicans are likely to filibuster the legislation.

Cutting off debate on the bill would likely ignite a major partisan firestorm, and top Democrats will look to make their move as fast as possible, according to the Democratic aides.

“This is not the kind of thing where we could have a long, drawn-out rollout. We’d have to say, Here’s the deal,’ and then get to the floor and get it passed before anyone can mobilize against it,— one leadership aide said.

The leadership aide argued that Speaker Nancy Pelosi (D-Calif.) would also have to agree to the deal before Reid would be willing to bring it to the floor, since any major changes to the bill in the House or in conference would likely make final passage impossible in the Senate.

Progressives and union leaders have largely been cool to the idea of a compromise that doesn’t include the union voting provision. When the latest proposal for moving an arbitration-only bill was floated, top union officials largely said they would support it, but only because they would reinsert the card-check provisions in conference.

Service Employees International Union President Andy Stern — who has participated in the Senate talks — said in a statement earlier this year that no matter what deal clears the Senate, the voting provisions would be included “in the final bill or by amendment in both houses of Congress.—

But Democrats said any deal that Harkin is able to get with moderates in the Senate will have to be the final word on the legislation — at least for now — and that no major changes could be made if it is expected to become law.

“It’s … the kind of thing that the House would have to eat,— a Democratic aide said, explaining that Democrats in the Senate will need union officials to make the case to Pelosi that she should pass the bill “as is.— The hope is that union officials will accept an imperfect bill as better than nothing.

But even supporters privately concede that the prospects for the legislation remain dim. Business groups have continued to press on the issue, even during the past several months after it appeared the legislation had died, and the National Right to Work Committee on Monday launched a new round of ads targeting moderate Democratic Sens. Jim Webb and Mark Warner of Virginia.