Retaking the Senate in 2018 was always a tough climb for Democrats because they are defending 10 seats in states that Donald Trump won in 2016. But that difficult terrain is looking a little less daunting these days, as new polling has led some election forecasters to believe several of those states are actually quite safely in Democratic hands.

Over the past few weeks, Democrats seem to have shored up their positions in Ohio, Pennsylvania, and Wisconsin. Sen. Sherrod Brown (D-OH) has a double-digit polling lead on his Republican opponent; Sen. Bob Casey (D-PA) was always the favorite but now appears absolutely safe; and Sen. Tammy Baldwin (D-WI) — maybe the most vulnerable of the bunch and up for her first reelection in a state Republicans had been dominating — also seems to be on solid ground.

It’s a sign of the times: After two new polls found Brown leading Republican Rep. Jim Renacci by 17 points, the University of Virginia’s Crystal Ball moved Ohio to Likely Democrat. On Thursday, they moved Pennsylvania to Safe Democrat after another pair of polls put Casey up by double digits over Republican Rep. Lou Barletta.

The biggest surprise might be Baldwin’s apparent security. As I previously explained, there was reason to think the first-term senator could be in trouble in Wisconsin, a state where the GOP has solidified control of the state government and made ousting Baldwin a top priority. Indeed, Gov. Scott Walker’s Republican allies had already spent $8.5 million against her in March.

But given the strong showing for Democrats in several special elections in the Badger State and new surveys that have shown Baldwin leading her potential opponents by 9 points or more, Baldwin is looking strong. Wisconsin is now a Likely Democratic win, according to the Crystal Ball’s Kyle Kondik:

On top of these election outcomes, Baldwin’s potential GOP opponents are not engendering much confidence from GOP leaders. Senate Majority Leader Mitch McConnell (R-KY) recently made headlines when he did not include Wisconsin and other purported Republican Senate targets on a list of key contests that he thought would determine control of the Senate

This tracks with other signs. Senate Republican leader Mitch McConnell did not include Wisconsin in his list of battleground states in an interview with the Washington Post. And Politico’s Burgess Everett detailed recently how the Senate map seems to be shrinking in favor of Democrats:

Opportunities to snag GOP-held seats are so scarce that Democrats could easily see multiple incumbents lose if the Trump backlash turns out to be weak. But for now, Senate Majority Leader Mitch McConnell (R-Ky.) agrees the Senate is in play and has not been bullish on knocking off senators like Sherrod Brown (D-Ohio) and Bob Casey (D-Pa.), who have both opened up double-digit leads, according to polls released this week. So far, there are no suggestions Sen. Debbie Stabenow (D-Mich.) faces any kind of trouble. One big clue on which states are truly in play came this week when the Democratic Senate Majority PAC placed fall ad reservations in Florida, West Virginia, Montana, Missouri, Indiana, North Dakota, Tennessee, Nevada and Arizona. For now, the group decided Brown, Casey, Stabenow and Sen. Tammy Baldwin (D-Wis.) don’t need extra help. Steven Law, who runs the McConnell-aligned Senate Leadership Fund, said that Democrats’ “target list is a lot like ours.”

Democrats are still at a disadvantage in trying to flip the 51-49 Senate. They have only two obvious opportunities to flip Republican-held seats — Nevada and Arizona — and they also have very vulnerable incumbents of their own in Missouri, Indiana, North Dakota, and West Virginia. Florida, where Democratic Sen. Bill Nelson is facing a well-funded campaign from two-term Gov. Rick Scott, also can’t be taken for granted. The polling there suggests a very close race.

But given the terrain they were facing, the latest trends in the Rust Belt are a good sign for Democrats if they’re going to pull off the unlikely.

“Republicans remain favorites to hold the Senate after the 2018 election in November,” Kondik wrote, “although there is a narrow path for Democrats to take the majority.”