Five weeks before Americans vote in the midterm elections, a nonpartisan analyst projects that Democrats could gain roughly 20 seats in the House and four or five in the Senate, while fresh Supreme Court rulings have handed the Trump administration one new tool for policing voter rolls and taken another away.

The estimates come from Charlie Cook, founder of the nonpartisan Cook Political Report, and were discussed Thursday by the CBC’s Washington correspondents, Katie Simpson, Willy Lowry and Paul Hunter, in a CBC Radio podcast. Some of the Senate races drawing the most attention are in Michigan, North Carolina, Alaska and Iowa, with control of Congress at stake and Republicans fighting to hold on.

Last Friday, the Supreme Court cleared states to use an expanded federal database that combines citizenship information with Social Security numbers and other sensitive data to hunt for noncitizens on the voter rolls, a temporary win for President Trump in his campaign against noncitizen voting.

The court also ruled against the administration, which wanted the Postal Service to screen mail-in ballots after state election officials had submitted them. Introducing new mail-ballot rules at this point, the court said, “would have wreaked havoc, sowed chaos,” Mr. Lowry said on the podcast.

Mr. Hunter framed the question hanging over the final stretch: with the numbers pointing toward the Democrats, would Mr. Trump “push extra hard in other ways to try to salvage a win out of all this,” whether by claiming voter fraud or by changing how people vote?

Ms. Simpson said Mr. Trump “has a clearcut history of trying to undermine integrity in elections,” pointing to the aftermath of Jan. 6, and argued that the federal data push could be used to knock people off registration rolls, forcing them to sign up again or miss deadlines. Elections in the United States are run by individual states, not the federal government. In one Texas county, she said, people were erroneously removed from a voter list.

She also raised the possibility of the administration sending ICE agents or military officials to polling stations, something, she noted, they cannot legally do.

Mr. Lowry said the president had been laying the groundwork since a primetime address over the summer about election integrity, claims largely refuted in the days that followed. “He is already trying to plant the seeds of doubt for sure,” he said. In his view, Democrats’ best strategy is to “get out the way and let this all unfold — let the price of gas keep rising.” He said the election was less a vote against Mr. Trump, who still holds sway over Republicans, than against his agenda, above all the U.S.-Iran war, which he described as a betrayal of a campaign pledge to avoid wars and a direct hit to Americans’ wallets.

Ms. Simpson said the midterms would test which route Democrats take toward 2028, with a slate of progressive candidates and a slate of moderate ones. And she offered a caveat drawn from the party’s own record: “Don’t underestimate the ability of a party with a lead to screw up a lead. The polls may suggest that the Democrats are gonna do very well ... but there is so much time, and we don’t know whether the Trump administration is gonna have any ability to disenfranchise voters.”