Robert Byrd, the 90-year-old West Virginia lawmaker, resigned on Friday as chairman of the Senate appropriations committee, intensifying a scramble for power in Congress that could reshape the contours of US business regulation.

Amid the flurry of activity prompted by Tuesday’s election, speculation mounted over the fate of Joseph Lieberman, a former Democrat turned independent, after Republicans revealed that the Connecticut senator was in talks potentially to abandon his loose alliance with the Democrats and side with the Republicans.