Washington (CNN) – Upwards of $1 million a day is expected to be spent on health care television ads this week, as interest groups work overtime to try to influence Congress before the House votes on President Obama’s top domestic priority.

Health care commercials all but vanished from the airwaves in late January after Republicans scored an upset victory in the Massachusetts special election to replace the late Sen. Edward Kennedy. Republican Scott Brown’s win gave the GOP the crucial 41st vote needed to sustain a filibuster to block passage of the Democratic health care reform bill.

Now, as Democrats try to pass the legislation later this week without Republican support, outside groups are weighing in.

Last year, special interest groups spent a combined $200 million just on TV ads as Congress struggled to agree on how to overhaul the nation’s health care system, said Evan Tracey, a CNN consultant and president of Campaign Media Analysis Group.

Ad spending hit a high in 2009 following last August’s raucous town hall meetings. “At its peak, advertising levels were exceeding $1 million a day,” Tracey said.

Tracey noted that during last week alone, interest groups spent a combined $600,000 on health care ads. The spending increased to about $600,000 by Saturday and very likely will grow to $1 million at the beginning of this week.

Among the many organizations taking to the airwaves: the U.S. Chamber of Commerce, American Future Fund, Americans United for Change and MoveOn.org.