Kamala Harris may help Sherrod Brown keep his seat. It’s been harder for him each time he’s run as the state of Ohio gets redder and redder. But he might just be able to hang on again if everything breaks just right: Democrats simply can’t hold their Senate majority without Brown. The brutal map means that Republicans only need to flip West Virginia — a near-certainty, with Sen. Joe Manchin (D-WV) bowing out — and not fumble their incumbencies in Florida and Texas to reach 50 seats. If they flip either Ohio or Montana, both states Trump won twice, they win the majority. Democrats are also defending in the perpetual battlegrounds of Pennsylvania, Wisconsin and Nevada, as well as fighting for open seats in Arizona and Michigan. […] “Take nothing for granted but if the urban electorates in Ohio and the young voters in Ohio are energized because of Harris-Walz, that’s life Sherrod needs,” former Ohio Democratic Party Chairman David Pepper told TPM. “The one thing that could kill him in November is a lack of enthusiasm on the Democratic side where the base doesn’t come out,” Dr. Dave Cohen, a professor of political science at the University of Akron, told TPM. “Kamala Harris replacing Biden was the best possible news that Sherrod Brown could have gotten.” Brown can’t win without the votes of at least some Trump supporters. But the stronger the showing from Democratic voters, the fewer of those crossovers he needs. That’s true even in a state Harris has…