Democrats do still have paths to retaining control. But they are increasingly narrow.
Look at the map this way. If Democrats can hold on in just one of the four following toss-up states — Colorado, Iowa, Arkansas, or Alaska — their hopes of holding the Senate remain alive. That is plausible. But a lot has to go their way after that.
Let’s give Republicans West Virgina, Montana, and South Dakota up front, while giving Democrats North Carolina, New Hampshire, and Michigan — outcomes that are consistent with the polling averages. If Dems can limit Republicans to wins in three of these four (CO, IA, AR, AK), that puts the GOP at 51 seats.
That would probably send us into overtime, with Louisiana and Georgia likely to head to run-offs due to election rules. To keep the Senate at a 50-50 split, Democrats would then have to win one of those run-offs (so they cancel one-another out) and Greg Orman would have to win in Kansas andhe would have to caucus with Dems. Without Kansas, Democrats would have to win both those runoffs. This is not entirely impossible. As Harry Enten has explained, recent history doesn’t tell us much about how these runoffs will go, and high African American turnout could scramble them. But it’s a very tall order, partly because the outcome of these red state run-offs would decide which party controls the Senate.
Alternatively: Democrats would have to win two out of the following four core toss-ups: CO, IA, AR, AK. This, too, is not an impossible outcome. Democrats trail by 2.1 points in Iowa and 1.5 in Colorado. As Nate Silverhas detailed, the polls only have to be a little off for Dems to win in such states. What’s more, there’s a great deal of uncertainty remaining: No one knows what sort of electorate will result from Colorado’s first experiment in all-mail balloting. Democrats insist mobilization efforts will enable Bruce Braley to close his small deficit in Iowa, a possibility that can’t be dismissed. Arkansas, which hasn’t been contested in recent presidential elections, has never seen this level of organization. (For these reasons, Dems winning one of these is plausible, too.)
Bottom line: Dems have to win 2 of the following 7 races: Colorado, Iowa, Arkansas, Alaska, Georgia, Kentucky and Kansas (with Greg Orman caucusing with the Dems) while winning in NC, NH, and Michigan. It's not impossible, but all seven favor the GOP right now.
Either way it's an uncertain, uphill battle that would only get the Dems to 50, with zero room for error.