Democrats are bullish about the November elections. They think they’ll win control of the House of Representatives, score big gains in the statehouses and run competitively in contests for U.S. Senate seats. But remembering 2016 causes some of them to wake up in the middle of the night wondering what could go wrong.

The optimistic expectations come from analyzing public opinion polls, weighing the advantages of out-of-power parties in midterm elections, comparing party fundraising and weighing other historical evidence. Based on factors like these, the prognosticators at FiveThirtyEight put the Democrats’ odds of winning the House at 82 percent.

Still, political due-diligence requires hard-headed analysis of potential problems that could arise in the final seven weeks before Nov. 6.

I put this to five of the most insightful Democratic strategists: pollsters Fred Yang, Jim Gerstein and John Anzalone; Mark Gersh, who for decades has been the maestro of analyzing congressional districts for House Democrats; and Paul Begala, a top party strategist since the 1992 Bill Clinton presidential run.

Yang, a partner in the Garin-Hart-Yang Research Group, is involved in some of the hottest races this year, including an unexpectedly close Tennessee Senate contest and a Kentucky House race pitting Amy McGrath, a Democratic ex-Marine combat pilot, against the Republican incumbent Andy Barr.

Yang said that a wave of support for Democrats is inevitable — “it’s not whether, but how big,” he declared — because “our voters are energized, theirs are not.” But he said he expects President Donald Trump to try to fire up Republican voters “with some manufactured crisis,” a factor that could affect the dynamics of the election.

Gerstein is the founding partner of GBA Strategies, which conducted polls in Ohio last month for Democrat Danny O’Connor before he came within a whisker of defeating the favored Republican Troy Balderson in a special election for a Republican House seat. There’s a rematch on the November ballot.

Gerstein said he’s anxious about the dozens of similar tossup races, almost all for Republican seats, which polls show as too close for accurate predictions. As the campaigns move into full gear, he said, Democrats will have cause for concern if they “don’t start putting some of these away.”

Anzalone is the Montgomery, Alabama-based president of Anzalone Liszt Research. His clients include Democrats competing in noteworthy gubernatorial races like the one in Florida featuring a Republican Trump enthusiast, Ron DeSantis, against a progressive-wing Democrat, Andrew Gillum. Anzalone frets about a “tsunami” of Republican money financing advertising blitzes and other tactics that could dominate the final weeks.

Democrats actually are matching Republicans on the money front, with an advantage in more than a few of the most competitive contests. But Anzalone fears that Republicans could reverse this advantage by tapping “a bottomless source of money” that will “come out at the end.”

Gersh worries about a torrent of negative personal assaults as Republicans discover that they can’t run successfully on any achievements. Attacking, he said, is a trademark of the Congressional Leadership Fund, the House Republican Super PAC run by the veteran GOP operative Corry Bliss.

Bliss last month disseminated a private federal security clearance form of Abigail Spanberger, a former anti-terrorism operative of the Central Intelligence Agency and now a Democratic House candidate in Virginia, apparently in hopes of making political use of Spanberger’s employment 15 years ago at a private Islamic school financed by Saudi Arabia. In 2003, while awaiting official employment at the CIA, Spanberger worked as substitute English teacher for the Saudi Embassy Academy in Virginia, something the CIA knew about. Bliss claimed that the information came from a routine request to the U.S. Postal Inspection Service, where Spanberger also briefly worked, which released it by mistake. Spanberger and Gersh don’t believe that.

Begala has campaigned all over the country for Democrats this year and found that they are emphasizing health care by stressing their support for protecting the Affordable Care Act from assaults by the White House and congressional Republicans. It’s been an effective strategy, Begala said, especially against the backdrop of Republican efforts to allow insurance companies to deny coverage or charge higher premiums to people with preexisting medical conditions.

So what’s he worried about? Republican-friendly distractions created by left-wing Democrats who have called for abolishing the Immigration and Customs Enforcement branch of the Homeland Security Department.

“I’m concerned that President Trump will try to bait Democrats into a false debate on abolishing ICE instead of a real debate on GOP efforts to abolish protections for people with preexisting conditions,” Begala said.

Albert R. Hunt is a Bloomberg Opinion columnist.