House Speaker Kevin McCarthy is a man who stays in motion — enthusiastically greeting tourists at the Capitol, dashing overseas last week to the G7 summit of industrial world leaders, raising funds back home to elect fellow Republicans to the House majority.

But beneath the whirlwind of activity is a stubborn standstill, an imbalance of power between the far-right Republicans who hoisted McCarthy to the speaker’s role yet threaten his own ability to lead the House.

It’s a political standoff that will be tested anew as the House returns this week from a long summer recess and McCarthy faces a collision course of difficult challenges — seeking to avoid a government shutdown, support Ukraine in the war and launch an impeachment inquiry into President Joe Biden.

“They’ve got some really heavy lifting ahead,” said the No. 2 Republican in the Senate, John Thune, of South Dakota.