Republicans hold a 53-47 Senate majority, meaning Democrats need a net gain of four seats to reach 51 and take control.

So let's take a look at the landscape, in order of most to least likely to flip. Tier 1 is most likely, Tier 2 is competitive but less likely, and so on. Race rating denotations (Toss-Up, Lean, etc.) are based on the Cook Political Report.

The map still favors Republicans, but Trump’s declining popularity --- particularly on the economy --- makes Democrats’ once long-shot bid to retake the Senate more feasible than ever before.

Newsweek’s tracker will be updated regularly as new polls, market odds, fundraising data, and race ratings are released.

Sen. Chris Murphy's defense of a candidate's Nazi tattoo highlights how far-left Marxist populism has become a Hydra overtaking the Democratic Party.