The CBS News head pollster has some information for Democrats expecting a Blue Wave to take over the House and more in November’s midterm elections: It’s not looking good.

In Where Did You Get That Number?, a new book out Tuesday from Simon & Schuster, author Anthony Salvanto, the CBS pollster, explains his methodology for tracking the 2016 presidential election, considered one of the biggest upsets in electoral history, and how those lessons apply for the coming season.

Studying the exit polls in 2016 for CBS News coverage of the presidential election, Salvanto saw what was happening – Hillary Clinton was losing ground, and voters who hadn’t cast ballots were not likely to vote for her. Salvanto delivered his verdict to the networks anchors and producers: “This is a contested race.”

The late deciders gave Trump the victory, Salvanto claims. CBS’s final 2016 poll gave him a big lead among voters who decided at the last minute.

Salvanto told the New York Post that comparing elections to horse races is wrong. “The horse-race analogy is compelling but it’s wrong. “In a campaign, everything can change tomorrow.”

Based on that perspective, Salvanto is relying on the lessons of 2016 to watch this year’s midterms. The CBS Battleground Tracker is looking at districts that will make a difference He told the Post: “Remember, in a midterm, you have to watch each congressional seat — don’t pay attention to national numbers.”

The CBS News Battleground Tracker has a panel of 5,700 registered voters, with the majority in the districts that are highly contested. That poll indicates that few House seats will change parties in November, with the GOP likely holding its majority in the House.

“Right now I think this election looks like a toss-up,” Salvanto said to the Post. “We see a Democrat pickup in the House of Representatives in the 20-odd seat range, but Republicans could certainly hold on to the House.”