Senators have warned they will not be bullied into supporting the government's new legislation on water charges.
The Seanad could defeat the Water Services Bill when it comes before it later this week - and force a three-month delay on a new regime coming into effect.
Fianna Fail and Sinn Féin have both indicated that they will oppose the Bill - meaning its fate will be determined by the dozen non-party senators, who could defeat it if they all vote against it.
Another possibility is the idea that the independents could force through some amendments to the legislation, which would then force the Dáil to accept them or else trigger the three-month hold.
But the government says any delay in implementing the new laws will only mean higher water bills for homes - which would then arrive in January instead of April.
The first Seanad vote, expected on Thursday, could pose the biggest threat yet to Fine Gael and Labour's ability to govern and pass laws.
Our political correspondent Gavan Reilly filed this report for Today FM's National Lunchtime News:
