A spokesman for Sen. Mark WarnerMark WarnerObama's last law: TALENT Act will enhance government efficiency GOP, Dems hear different things from Trump Decaying DC bridge puts spotlight on Trump plan MORE (D-Va.) said Wednesday it is "premature" to say whether the freshman senator will support the Employee Free Choice Act (EFCA).

"No one knows what the bill may look like when it gets to the floor, so the cloture question is premature," Warner spokesman Kevin Hall told The Plum Line's Greg Sargent.

Warner had written constituents in late March saying he believed "EFCA should be debated and voted upon by the Senate," lending supporters of the bill in the organized labor movement the impression that the centrist Democrat would at least support ending debate on the legislation.

Supporters of EFCA (or "card check") have experienced some setbacks in their effort to push the organizing bill through the Senate. In recent weeks, Sens. Arlen Specter (R-Pa.) and Blanche Lincoln (D-Ark.) have backed off from supporting the bill in its present form, and other Senate lawmakers have wavered on their support for the legislation.