Republicans got a key win that keeps alive their chances of needing only 51 votes to pass healthcare reform.

The Senate parliamentarian ruled Wednesday in Republicans' favor in a dispute with Democrats over part of a healthcare bill, according to a Senate leadership aide. The ruling means it can move forward and be amended for a possible vote next week with Republicans needing only 51 votes instead of the 60 needed to break a filibuster.

The dispute centered on the deficit reductions that are mandatory for a bill to use the procedural move called reconciliation. A bill has to meet certain requirements to be considered under the tool.

Chief among those requirements is that it reduces the deficit by a certain amount. In the health bill's case, the two committees of jurisdiction for the health bill each has to reduce the deficit by $1 billion. Those committees are Senate Finance and Senate Health, Education, Labor and Pensions.

The challenge from Democrats focused on the repeal of cost-sharing payments to insurers to reduce co-pays and deductibles for low-income Obamacare customers, according to a report in Congressional Quarterly, which first reported the ruling.

Democrats said the cost-sharing payments fell under the Senate Finance Committee's jurisdiction, and Republicans argued they belonged under the HELP Committee.

The parliamentarian ruled that the cost-sharing payments fall under Senate HELP, meaning that the bill meets the deficit reduction targets laid out in reconciliation instructions passed earlier this year.

The bill is expected to significantly change and be amended before it reaches the floor for a final vote. Major changes expected include restoring cost-sharing payments for two years.