Washington, D.C. (AP) – Congressional Republicans achieved a significant triumph this summer by passing President Donald Trump’s major tax and spending cuts without any support from Democrats. As they return to Washington this fall following a monthlong August break, they face the challenge of collaborating with Democrats — or finding ways to bypass them — as a government shutdown looms.

The annual spending battle is set to dominate the September agenda, along with a potential initiative by Senate Republicans to modify their chamber’s rules to prevent Democratic delays on nominations. The Senate is also contemplating proceeding with legislation imposing hefty tariffs on some of Russia’s trade partners as the U.S. applies pressure on Russian President Vladimir Putin concerning Ukraine.

In the House, Republicans will persist in their investigations of former President Joe Biden while Speaker Mike Johnson steers through divisions within his party over whether the Trump administration should release additional documents related to the Jeffrey Epstein investigation.

A look at what Congress will be doing as lawmakers return from the August break:

Keeping the Government Open

The most pressing responsibility for Congress is to avert a government shutdown by Sept. 30, when federal funding expires. It remains uncertain if Republicans and Democrats can reach an agreement on how to prevent this.

Congress needs to pass a temporary spending measure to keep the government funded for a short period while they work on the complete annual package. However, Republicans will require Democratic votes for an extension, and Democrats will demand substantial compromises. Senate Democratic Leader Chuck Schumer’s support of the Republicans’ measure to prevent a shutdown in March met with sharp criticism within his party.

The Trump administration’s moves to reclaim previously approved spending could further complicate negotiations. Republicans enacted legislation this summer that revoked about $9 billion in foreign aid and public broadcasting funds, and Trump informed Congress again on Friday of his decision to block $4.9 billion in congressionally approved foreign aid.

Democrats have warned that such efforts could tank the broader negotiations. “Trump is rooting for a shutdown,” Sen. Chris Murphy, D-Conn., posted on social media Friday.

Senate Nominations Fight

Senators are expected to return to Washington right where they left off in early August — fighting over Trump’s nominees.

Exasperated Republicans fled Washington for the month after making little headway with Senate Democrats over their nominations blockade, which has forced delays in confirmations and angered Trump as many of his administration’s positions remain unfilled. Republican leaders called it quits after a rare Saturday session that ended with a breakdown in bipartisan negotiations and Trump posting on social media that Chuck Schumer could “GO TO HELL!”

Republicans now say they’re ready to try and change Senate rules to get around the Democratic delays, and they are expected to spend the next several weeks discussing how that might work.

Russian Sanctions

Republican Sen. Lindsey Graham of South Carolina, one of Trump’s closest congressional allies, has pushed the president for months to support his sweeping bipartisan sanctions bill that would impose steep tariffs on countries that are fueling Russia’s invasion of Ukraine by buying its oil, gas, uranium, and other exports. The legislation has the backing of 85 senators, but Trump has yet to endorse it, and Republican leaders have so far said they won’t move without him.

Graham has stepped up his calls after Trump met with Russian President Vladimir Putin and Ukrainian President Volodymir Zelenskyy last month in hopes of a peace deal. Since then, Russia has continued to step up attacks on Ukraine.

“If we don’t have this thing moving in the right direction by the time we get back, then I think that plan B needs to kick in,” Graham said of his bill in an interview with The Associated Press last month.

Oversight of the CDC

Health and Human Service Secretary Robert F. Kennedy will appear before the Senate Finance Committee to discuss his health care agenda on Thursday, less than a week after he ousted Susan Monarez as director of the Centers for Disease Control and Prevention. Several other top officials also resigned in protest.

Kennedy has tried to advance anti-vaccine policies that are contradicted by decades of scientific research. Monarez’s lawyers said she refused “to rubber-stamp unscientific, reckless directives and fire dedicated health experts.”

Louisiana Sen. Bill Cassidy, the Republican chairman of the HELP panel that oversees the CDC and a member of the Finance Committee, has called on the CDC to delay a meeting of outside experts who make recommendations on the use of vaccines until Congress can look into the issue.

Divisions over Epstein

The House left Washington in July amid disagreements among Republicans about whether they should force President Donald Trump’s administration to release more information on the sex trafficking investigation into the late Jeffrey Epstein. The pressure for more disclosure could only get more intense when lawmakers return.

Democratic Rep. Ro Khanna of California and Republican Rep. Thomas Massie of Kentucky are pushing the House to take up their bill to force the Department of Justice to publicly release its investigation. They are planning a news conference this week joined by Epstein victims. The House Oversight Committee is also investigating the issue.

Democrats are eager to keep pressing on the Epstein files, especially after the Trump administration reneged on pledges for transparency. The case for years has been the subject of online conspiracy theories and speculation about who may have been involved or aware of the wealthy financier’s abuse.

Investigating Biden

The House Oversight Committee will return from August recess with a slate of interviews lined up as part of its investigation into former President Joe Biden’s mental state while in office. The committee has already conducted interviews and depositions with nearly a dozen former top Biden aides and members of the president’s inner circle.

The Republican-led committee will hear from former top Biden staffers in September like Jeff Zients, Biden’s final White House chief of staff, Karine Jean-Pierre, the former White House press secretary, and Andrew Bates, a top press aide.

Oversight Chair James Comer, R-Ky., has said public hearings and a full report can be expected sometime in the fall.

Stock Trading Ban

Congress has discussed proposals for years to keep lawmakers from engaging in trading individual stocks, nodding to the idea that there’s a potential conflict of interest when they are often privy to information and decisions that can dramatically move markets.

That push is now gaining momentum. A Senate committee has approved legislation from GOP Sen. Josh Hawley of Missouri that would also extend the prohibition on stock trading to future presidents and vice presidents — while notably exempting Trump. In the House, several members are putting forward proposals and even threatening to maneuver around GOP leadership to force a vote.

Still, there is plenty of resistance to the idea, including from many wealthy lawmakers who reap dividends from their portfolios.