Pennsylvania Senate Race shifts to "toss-up" with 15 days to go

• Ohio, Michigan and Wisconsin are the three other toss-up Senate races at this point.

Driving the news: Cook shifted the Pennsylvania race to "toss-up" from "Lean Democrat" on Monday, saying it's a margin of error race among internal polling.

• Sen. Bob Casey (D-Penn.) leads GOP challenger Dave McCormick by just under two percentage points in the RealClearPolitics average of polls. Casey previously led by wider polling margins.

Zoom in: Cook also shifted the Nebraska Senate race from "Likely Republican" to "Lean Republican."

• The service cited Independent challenger Dan Osborn's viral ads and the tightening polls with incumbent Republican Sen. Deb Fischer.
• It also said Fischer's re-election fight looks more like the Texas Senate race, where Sen. Ted Cruz faces a tough fight from Rep. Colin Allred, than it does of the not-as-close Florida Senate race.