According to Real Clear Politics' average of the key polls, only seven Senate seats are true "toss ups" — and to take control of the chamber, the Democrats have to win all seven. To make matters worse for Democrats, the so-called "Kavanaugh effect" appears to be real and seems to particularly impacting a few of those toss-up seats.
RCP currently gives Republicans 49 seats that are either "safe" or not up for reelection. Prior to the Kavanaugh allegations, that number was 47. Meanwhile, the Democrats safely have 44 seats, which means they need to win all seven of the remaining toss ups to gain the 51-seat majority in the Senate. Post-Kavanaugh, that prospect is looking less and less likely.
Tennessee's open seat is one of those "toss ups," but surging support for Republican Marsha Blackburn is moving it rapidly in the direction of "leaning" Republican. Democrat Phil Bredesen once enjoyed a five-point lead, but after the Kavanaugh chaos, multiple polls show Blackburn leading by a significant margin. A Fox News poll found Blackburn ahead by 5 points last week, while a CBS News/YouGov poll found her leading by 8 points. A New York Times Upshot poll this week found Blackburn ahead by 14 points.
Bredesen created a stir when he came out in support of Kavanaugh before the vote. Many have interpreted it as a political ploy, with a recent undercover video suggesting as much, but it appears to not have worked in his favor, with many Democrats expressing disgust at the move.
Arizona's open seat has also recently started trending in the Republican's direction. A recent ABC 15/OH Predictive Insights poll found Republican Martha McSally leading Democrat Kyrsten Sinema by 6 points. But another recent poll by CBS News/YouGov found Sinema ahead by 3 and a Fox News poll gave the Democrat a 2-point lead.
In Missouri, Republican Josh Hawley currently holds a razor-thin edge over Democrat Claire McCaskill (46 - 45.6).
After multiple polls showing him trailing his Democrat opponent pre-Kavanaugh, Nevada Republican Dean Heller is currently tied with Democrat Jacky Rosen.
The race in Indiana between Republican Mike Braun, Democrat Joe Donnelly, and Libertarian Lucy Brenton is also extremely tight, with Donnelly currently holding just a 2.5-point lead over Braun (43.5 - 41). Libertarian Brenton is taking 7 percent of the vote.
The other two toss-up seats are Montana, where polls from mid-September show Democrat John Tester holding the edge by just 3 points, and Florida, where late September polls gave Democrat Bill Nelson a narrow 2.5-point lead over Republican Gov. Rick Scott.
If RCP is correct about the seats safely held by the Democrats and Republicans, if just one of these toss-up seats goes to the Republicans, Democrats will fail to gain the 51-seat majority. If two go to Republicans, the balance of power in the Senate remains unchanged.