In a blow to the White House, the Senate's top Democrat signaled Tuesday that Congress may fail to meet a year-end deadline for passing health care legislation, leaving the measure's fate to the uncertainties of the 2010 election season.

Majority Leader Harry Reid, D-Nev., spoke as Democratic officials said it could be December before Senate debate begins in earnest on the issue atop President Barack Obama's domestic agenda, months after senior lawmakers and the White House had hoped. The drive to pass legislation has been plagued for months by divisions within the party's rank and file.