The GOP’s outlook in Arizona and North Carolina is also looking gloomier. Both Sen. Martha McSally of Arizona and Sen. Thom Tillis of North Carolina are facing nuisance primary challengers, which makes it harder for the incumbents to consolidate their base. But the more they try to protect their right flank, the tougher it becomes to win over the suburban moderates who decide races in these swing states.

McSally, who lost last year’s election before being appointed to her seat, trailed Democratic challenger Mark Kelly by 5 points, 46 to 41 percent, in a poll taken in August. She’s been outraised in all three of the fundraising quarters by significant margins—an unusual disadvantage for a sitting senator. She already lags Kelly in campaign cash by nearly $4 million.

Tillis holds the lowest approval rating (33 percent) of any sitting senator, according to the Morning Consult survey. A Democratic poll conducted in September found him trailing his little-known Democratic opponent Cal Cunningham, 45 to 43 percent. But before he even faces Cunningham, he’ll have to get past self-funded businessman Garland Tucker in the primary. Tucker has poured $1.2 million of his own money into the campaign—around the same amount Tillis raised in the last three months. Tucker has already been using that money on anti-Tillis campaign ads, forcing the senator to respond in kind.