The latest Washington Post-ABC News tracking poll shows Donald Trump and Hillary Clinton in a virtual dead heat nationally. (Peter Stevenson/The Washington Post)

The Hillary Clinton email controversy has given down-ballot Republicans something they badly need in the final days of the election: an opportunity to go on offense and talk about something other than Donald Trump.

“Hillary Clinton’s latest chapter in her ongoing email scandal, saga, is just a reminder of how much corruption there is in Washington and how disturbing this is,” the embattled Sen. Patrick J. Toomey (R-Pa.) told voters this week at a diner in the town of Media, near Philadelphia.

He noted that the administration of Pennsylvania Gov. Tom Wolf (D) is resisting a court order to release more than 50,000 emails that Toomey’s Democratic opponent, Katie McGinty, sent while she was the governor’s chief of staff. “Her devotion to Hillary Clinton is so complete that now she’s decided that she has to have her own email scandal,” Toomey said.

McGinty, left, and Toomey, right, at an Oct. 24 debate in Philadelphia. (Photos by Matt Rourke/AP)

As recently as a week ago, the Republicans’ chances of holding on to the Senate appeared to be slipping away.

Individual GOP candidates’ efforts to distance themselves from Trump were being overwhelmed by the furor over an 11-year-old video in which the nominee boasted of kissing and groping women without their consent, and the subsequent claims by a procession of women that he had actually committed such acts.

Last Tuesday, the nonpartisan Cook Political Report, which had earlier predicted that Republicans would manage to keep their Senate losses low, shifted to a projection that the Democrats would pick up five to seven seats — enough to regain control of the chamber. In the last 15 public polls, all in October, Pennsylvania’s Senate race has been nearly deadlocked: Three showed a tie, four had Toomey ahead and seven gave McGinty an edge, with most of those leads being within the margin of error.

But now, Republicans see a chance to change the subject and remind voters of the drama and perceived moral ambiguity that has surrounded the Clintons for more than a quarter-century.

Republicans could hardly have conjured a better “October surprise” than the revelation that a trove of emails belonging to close Clinton aide Huma Abedin had turned up on the laptop of Abedin’s husband, former congressman Anthony Weiner (D-N.Y.), who is under investigation over sexually suggestive texts he allegedly sent to a 15-year-old girl.

However the latest FBI investigation of Abedin’s emails turns out, the fact that they are even at issue goes back to Clinton’s initial misjudgment in setting up a private email account and server. And that can be traced to the secretive impulses that have so often driven the candidate and her inner circle.

“This is what life with the Clintons look like,” House Speaker Paul D. Ryan (R-Wis.) told Fox News on Tuesday. “There’s always a scandal, one after another. There’s an investigation.”

“So they can’t win,” he added, “and she can come in with a Democratic Congress — worst of all possible things — if Republicans do not turn out and do not vote.”

Though it is an implicit acknowledgment of the fact that the Democrat remains more likely than not to win the White House, Republicans are seizing upon an argument that they must retain control of Congress to be a check on Clinton — not only on her agenda but on the behavior of her administration.

“We used to say in prosecution, it’s primacy and recency. The closing argument reintroduces all of the most pertinent issues,” said Rep. Patrick Meehan (R-Pa.), who was campaigning with Toomey.

“Look at this,” Meehan said in reference to the latest email controversy. “This is almost the personification of the trust issue.”

The email issue may also have the effect of helping to unify Republicans, who have been divided over Trump.

Don Chesnet, 71, a retired small-business man, explained his views of Trump and Clinton, respectively: “You either have scum or you have a criminal.”

He added that “scum” might not rub off, while criminal behavior was an affront to taxpayers.

Even a small shift in the political breeze could have a big impact on the Senate races, said Charlie Cook, editor and publisher of the Cook Political Report.

“There are six races that are just teetering on the edge, where it wouldn’t take much to tip several of them the same way,” Cook said.

He added that there is a significant slice of the electorate that is voting for Clinton primarily because they find Trump unacceptable.

“They don’t like her, don’t trust her and would rather not vote for her but feel they have no choice,” Cook said. “There are a lot of voters who would certainly like to hedge [that vote] a little bit.”

Some Democrats worry that they have seen all this before — the last time that someone named Clinton was their standard-bearer.

In 1996, Bill Clinton was cruising to reelection when a controversy exploded over the fact that Democrats had been taking large donations from foreign entities that are forbidden from donating to U.S. campaigns. A number of those illegal donors had access to the Clinton White House.

“That’s a good parallel” to the effect that the resurgent email controversy could have today, a senior House Democrat said, requesting anonymity to discuss the downbeat feeling some have.

In 1996, Bill Clinton’s big lead held up, although he remained under 50 percent and House Democrats — who had hoped to bounce back into the majority after their disastrous 1994 showing — picked up fewer than five seats and remained in the minority for a decade to come.

The 42nd president also had a contentious relationship with the FBI director at the time, Louis Freeh — and such a drama could play out again with another Clinton in the Oval Office. Hillary Clinton and her top campaign officials have been highly critical of the unusual decision by FBI Director James B. Comey to go public Friday with the fact that the bureau had resumed its investigation of the emails.

All of which gives voters a new set of crosscurrents to navigate as Election Day draws near.

For down-ballot Democrats, Sharon Jankauskas is their nightmare. The 60-year-old nurse practitioner, who attended Toomey’s campaign event in Media, said she sees the presidential races as the “lesser of two evils.”

She plans to vote for Clinton but is also pulling for Toomey. She also likes Clinton’s running mate, Sen. Tim Kaine (D-Va.).

So Jankauskas is looking for what, in her view, is a silver lining to electing Clinton: “We can always impeach her and get her out.”

All of which raises the possibility that another Clinton in the White House could bring a reprise of the political culture of the 1990s, when a Republican Congress was constantly investigating the Clintons.

Americans have already gotten a foretaste. when the congressional panel investigating the 2012 attacks on a U.S. diplomatic post in Benghazi, Libya, helped uncover the fact that Clinton had been using a private email address and server when she was secretary of state.

Rep. Trey Gowdy (R-S.C.) told CNN that if Clinton is elected, Congress will continue its scrutiny.

“The legislative branch does have an obligation to provide oversight,” Gowdy said.

Correction: An earlier version of this article incorrectly identified Sen. Patrick J. Toomey as a Democrat. He is a Republican.