A funny thing happened in recent days: Even as Donald Trump appears to have some momentum in the presidential race, the GOP's odds of holding the Senate appeared to diminish — at least somewhat.

The GOP's effort to hold the Senate has always been a tough slog, even if it remained competitive at the top of the ballot. And sure enough, despite Trump not appearing to have dragged down his fellow Republicans too much (if at all), the GOP finds itself with what seems to be an increasingly uphill battle to retain the Senate, with five days left.

Today we're making no major adjustments to our Senate race ratings, but some of our “toss-up” races seem to be getting a little friendlier for Democrats.

Starting with Nevada. We're not quite moving this to “lean Democratic,” but we were tempted. Public polling there remains very competitive; Republican Rep. Joe Heck even led in one poll — from CNN — this week, and he was up by seven points in an NBC-Wall Street Journal-Marist poll last week. But Republicans, Democrats and those watching the race closely feel as if this one nominally favors Democrats and former Nevada attorney general Catherine Cortez Masto right now. It's a state where Trump appears to be losing ground, and Democrats have done very well in all-important early voting — about on par with how they did in 2012, when President Obama won the state by six points.

Of course, it bears noting that in that same 2012 election that Obama carried the state, appointed GOP Sen. Dean Heller also won, by one point. So it's clear Heck still has a shot. But those numbers certainly don't help him.

Were Cortez Masto to win the seat, which retiring Senate Minority Leader Harry Reid (D) is vacating, it would prevent Democrats from losing any seats in the 2016 election and make their path to a majority in the chamber significantly easier. From there, they would have to win only two of the five other seats we currently rate as “toss-ups,” or only one of the five if they can pull an upset and defeat Sen. Marco Rubio (R) in Florida, which we currently rate as “lean Republican” but is close.

The second seat that is looking tough for the GOP is Pennsylvania. Democrat Katie McGinty has led in the past nine polls here — including by three to six points in a trio of good polls released this week.

Via RealClearPolitics

It's a little more difficult to push this into the light-blue column, though, for a couple of reasons: 1) Sen. Pat Toomey (R) has the advantages of incumbency, and 2) the presidential race here is tightening. And sure enough, a poll out Thursday from Quinnipiac University has him within one point — his closest result in 10 polls.

The third “toss-up” seat that is giving Republicans heartburn right now is that of Sen. Roy Blunt (R-Mo.). It has steadily climbed our list of the 10 Senate races most likely to change parties, and since we put it at No. 6 last week, two new high-quality, nonpartisan polls show Blunt leading Democratic Secretary of State Jason Kander by just one point. One of those polls even had Trump carrying the state by 14 points, and were Blunt to lose a state that Trump carried, it would be a particularly hard pill for the GOP to swallow.

It's entirely possible that Republicans could still hold the Senate come Tuesday. But the races that are going to decide that just aren't moving in the right direction for them right now.