WASHINGTON — Across-the-board spending cuts all but certain, Republicans and Democrats in the Senate are staging a politically charged showdown designed to avoid public blame for any resulting inconvenience or disruption in government services.

The two parties drafted alternative measures to replace the cuts, but officials conceded in advance the rival measures were doomed.

At the White House, President Barack Obama invited congressional leaders to discuss the issue with him on Friday — deadline day for averting the cuts, which would slash $85 billion from the military and domestic programs alike.