With the exception of the Labor Party, all major parties in the Netherlands have a shot at winning’s Wednesday’s provincial elections, polls show.

The local elections are nationally relevant because provincial deputies will indirectly elect the members of the Senate in May. Prime Minister Mark Rutte’s ruling coalition could lose its razor-thin majority in the upper chamber.

Rutte’s liberals are still ahead in the polls and could win twelve seats according to a poll aggregator published by the national broadcaster NOS.

The Christian Democrats, the liberal Democrats, the nationalist Freedom Party and the far-left Socialist Party are each projected to win ten or eleven seats. Given the margin of error, however, and the difficulty of translating provincial votes into Senate seats, the five parties are virtually tied.

The ruling Labor Party is expected to lose half its seats. National opinion polls show it to be deeply unpopular. Left-wing voters are disappointed Labor joined Rutte’s right-wing party in a coalition and are defecting to either the centrist liberal Democrats or the hardline Socialists.

38 seats are needed for a majority in the Senate, usually a sleepy constitutional body that can only send legislation back to the lower chamber. Most senators are retired politicians or grandees who toe the party line.

However, in December three Labor Party senators unexpectedly broke party discipline to vote down a major health reform bill, triggering a cabinet crisis.

Labor earlier threatened to hold up rent reforms in the Senate and last month called for deeper cuts in natural gas production than the government had proposed.

Rutte’s liberals were forced into a coalition with their Labor rivals in 2012 when the two parties got over 50 percent support together in parliamentary elections. Lacking a majority of their own in the Senate, they formed an informal alliance with the liberal Democrats and two small Christian parties.

No recent poll has shown the five parties winning 38 Senate seats or more. Rutte may have to do a deal with the Christian Democrats — who traditionally do well in local elections — to save his government.

Although the Christian Democrats have quietly backed the majority of the government’s program, they have been vocal in their opposition to signature reforms such as the decentralization of child and elderly care and higher taxes. They would probably condition their support on tax relief which would necessitate deeper spending cuts than Labor is likely to tolerate.