WASHINGTON — Lawmakers return to Washington this week for an abbreviated election-season session in which they are expected to do the bare minimum, including passing a short-term budget bill and dealing with the Zika outbreak.

All Congress must do this month is keep the government from shutting down Oct. 1 and, with any luck, provide money for the fight against the mosquito-borne Zika virus.

Republicans controlling Congress promise they won’t stumble on those matters now, but the weeks ahead could prove tricky.

A chief motivation for the September session, especially for Senate majority leader Mitch McConnell, a Kentucky Republican, is allowing lawmakers to return to campaigning as soon as possible. Republicans are scrambling to hold onto their Senate edge as GOP 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 — as does President Obama — 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, a Nevada Democrat.

Lawmakers left Washington seven weeks ago without resolving a dispute about 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.

Because the shutdown-prevention measure simply has to pass, it’s a tempting target for lawmakers seeking to use it as a vehicle for their preferences. For instance, Senator Bill Cassidy, a Republican from Louisiana, is pressing for emergency grants to help communities in his flood-ravaged state to recover.

‘‘I hope we can accomplish that in September,’’ Cassidy said.

But GOP leaders probably will try to keep the spending bill as free of unrelated additions as possible, especially now. If GOP leaders were to grant Cassidy’s request, it would make it more difficult to say no to others, such as Democrats seeking money for fixing the lead-tainted water system of Flint, Mich.

House conservatives are looking to press ahead with impeaching IRS Commissioner John Koskinen over the destruction of agency e-mails and misleading testimony on whether the tax agency, before his arrival, improperly scrutinized conservative groups seeking nonprofit status.

The impeachment drive is a headache for Republicans who believe that Koskinen’s conduct isn’t serious enough to warrant impeachment but who might be reluctant to back the Democratic appointee in such a politically charged environment.

In a recent memo, House majority leader Kevin McCarthy, a California Republican, said lawmakers will take up legislation regarding the Obama administration’s $400 million payment to Iran in January, made immediately after four US prisoners were released.

The payment, for undelivered arms to the shah of Iran, was made on the same day of the prisoner release, and Republicans call it ‘‘ransom.’’ The as-yet-unreleased legislation is designed to prevent a repeat, but seems like an election-season messaging effort.

A House-Senate conference committee is trying to finish work on a defense policy bill that could require young women to sign up for the draft for the first time.

McConnell also wants to advance a popular water projects measure. But the priority is to simply adjourn the chamber to allow embattled incumbents such as Republican Senators Kelly Ayotte of New Hampshire, Pat Toomey of Pennsylvania, and Richard Burr of North Carolina to get back home and campaign for reelection against the political headwinds created by Trump.

The abbreviated session should give GOP-run committees a final preelection chance to hold hearings on the Obama administration and other targets such as EpiPen manufacturer Mylan.

That company has come under withering criticism for steep price increases for its lifesaving injector, which can stop potentially fatal allergic reactions to insect bites and stings, and foods such as peanuts and eggs.

House Republicans are promising hearings on Hillary Clinton’s e-mails. FBI Director James Comey criticized Clinton’s use of a homebrew e-mail server to handle sensitive work-related e-mails as ‘‘extremely careless’’ but said his agency’s yearlong investigation found no evidence of criminal wrongdoing.Republicans now are demanding that the Justice Department open a new investigation into whether Clinton lied during testimony last year before the House Benghazi committee. They claim the FBI note might show Clinton provided inconsistent answers to questions about her handling of e-mails containing classified information.

While Trump publicly maintains support from numerous high-ranking GOP officials, a significant number of discussions among Republicans in Washington often begin with an assumption that Clinton will be president come January.

Trump advisers vigorously dispute that the race has slipped from their grasp. They contend most Americans are just now tuning into the presidential campaign in a serious way.

‘‘We’re very much on schedule to do what we need to do to turn out the vote for Mr. Trump,’’ said Bob Paduchik, Trump’s Ohio state director and one of the most experienced operatives on the Republican’s staff. Paduchik said Trump’s efforts heading into the fall are focused primarily on rallying ‘‘disaffected Democrats and independents.’’