Jennifer Duffy, who handicaps Senate races for the nonpartisan Cook Political Report, has both Arizona and Tennessee in the “tossup” category. Late last week, she moved Texas from “likely Republican” to “leans Republican,” upgrading the chances of an upset by Beto O’Rourke, the Democratic challenger to Ted Cruz. “I just can’t ignore Texas anymore,” she told me. “O’Rourke has too much money.” It’s largely small donations from individual donors, underscoring the romance of his bid and the contrast between him and Cruz, who’s not exactly romantic.

Democratic leaders have, among other smart adjustments, ramped up their digital efforts with an eye toward the youngest voters, whose turnout is typically disappointing but whose distaste for Trump is strong. The party’s problem — a huge one — is that 10 of its incumbents are in states that voted for Trump. It can’t afford for more than one or two to lose.

The four in Rust Belt states where Trump prevailed by single-digit margins — Michigan, Pennsylvania, Wisconsin and Ohio — seem for now to be safe, amid signals of disenchantment with Trump in that region.

North Dakota, Montana, Indiana, Missouri and West Virginia all favored Trump by double-digit margins. But in none of them has the Republican challenger yet proved especially mighty. In Montana and in West Virginia, where a Democratic “super PAC” spent heavily and successfully to keep the Republican candidate it considered most worrisome from getting the nomination, the Democratic incumbents are looking sturdier every day.

Florida, where Trump edged out Hillary Clinton, will be noisy and nasty. Bill Nelson’s Republican challenger is the state’s governor, Rick Scott, who’s willing to pump his own millions into the race. But both the Democratic megadonor Tom Steyer and the American Civil Liberties Union are engaged in initiatives that could elevate Democratic turnout there. And Scott’s two gubernatorial victories were mere one-point wins in midterm years — 2010 and 2014 — when Republicans swaggered. In 2018, they’re slinking.

Some Republicans believe that they can snatch the Senate seat held by Robert Menendez, a New Jersey Democrat who was ensnared in a humiliating ethics scandal. Democratic leaders aren’t all that worried, and Duffy sides with them.