WASHINGTON — Lawmakers return to Washington this week for an abbreviated election-season session in which they will likely do what they do best: the bare minimum. All Congress must do this month is keep the government from shutting down on Oct. 1 and, with any luck, finally provide money for the fight against the mosquito-borne Zika virus. Republicans controlling Congress promise they won’t stumble now, but the weeks ahead could prove tricky.

A chief motivation for the September session, especially for Senate Majority Leader Mitch McConnell, R-Ky., is allowing lawmakers to return to campaigning as soon as possible. Republicans are scrambling to hold onto their Senate edge as presidential nominee Donald Trump lags in the polls.

The short-term spending measure is sure to pass. The alternative is that Republicans would get the blame for a government shutdown, as they did in 2013.

But it’s a complicated path for the temporary spending bill. Some House conservatives say the measure should last into next year, when there is a new president and a new Congress, and that would block any chance for a session after the Nov. 8 election. Leaders in both parties feel otherwise, and a temporary measure until December seems to be the consensus.

“We are not doing anything into next year and every Republican should be aware of that right now,” said Senate Minority Leader Harry Reid, D-Nev.

Lawmakers left Washington seven weeks ago without resolving a dispute over money for Zika. The virus can cause severe birth defects and is linked to a host of other maladies. Obama asked Congress in February for $1.9 billion in emergency money, but legislation to partially pay for his proposal collapsed in July amid various fights. Among them was a Republican provision to deny money to Puerto Rican affiliates of Planned Parenthood.

The abbreviated session should give Republican-run committees a final pre-election chance to hold hearings on the Obama administration and other targets such as EpiPen manufacturer Mylan, N.V. That company has come under withering criticism for steep price increases for its life-saving injector.