It’s just a midsummer snapshot, but viewed as the latest of a series of snapshots in a trendline, Democrats are in decent shape to hold their Senate majority at this political moment, according to recent polls. Put another way, it could be a lot worse for Dems, considering the number of seats they have to defend compared to the GOP (21-15).
From Harry Enten’s take at FiveThirtyEight:

If Democrats win all the states in which the polls now favor them, the party would lose four seats (Alaska, Louisiana, Montana and West Virginia) and pick up Georgia. Add on a probable loss in the Senate race in South Dakota (which isn’t included here because it’s a three-way matchup), and Democrats will hold on to a 51-to-49 seat majority in the next Senate. Sum up the probabilities of each race, and Democrats end up with about 50 seats, on average, in the new Senate. That would be good enough for them to keep control of the chamber, with Vice President Joe Biden acting as a tiebreaker.
…In other words, the final outcome for the Senate could be anything from a minor Republican gain to a GOP romp. At the moment, the state of play seems manageable from a Democratic perspective, but the party’s position is perilous. A tiny shift could tip the canoe and spill a lot of Democrats overboard.

We knew about the ‘perilous’ party position already. However, Dems being competitive at midsummer, given the number of exposed senate seats, is a lot worse for Republicans than they had hoped. A narrow victory or loss is pretty dicey for them too. And with Democratic candidates leading in some polls in states like GA and KY, where their senate leader is in danger, something isn’t working for the GOPs.
At NBC First Read Chuck Todd, Mark Murray and Carrie Dann observe:

…Our brand-new NBC/Marist polls of Colorado and Michigan show Sen. Mark Udall (D-CO) leading Cory Gardner (R) by seven points among registered voters, 48%-41%, in Colorado’s key Senate race. They find Gov. John Hickenlooper (D) ahead of GOP challenger Bob Beauprez by six points, 49%-43%. They have Rep. Gary Peters (D-MI) up over Republican Terri Lynn Land by six, 43%-37%, in Michigan’s Senate contest. And they show Gov. Rick Snyder (R) leading Democratic challenger Mark Schauer by two points, 46%-44%. So why are Udall, Peters, and Snyder all ahead in their contests? Here’s an explanation: mind the gaps — the gender gap, the Latino gap, and the independent gap. In Colorado, Udall is up by 12 points among female voters (50%-38%), as Democratic groups like Senate Majority PAC are up with TV ads (like this one) on abortion and contraception. Indeed, 70% of Colorado voters in the NBC/Marist poll said they were less likely to vote for a candidate who supports restrictions on the use of contraception. And in Michigan, Peters is ahead by 13 points with women (46%-33%).
We’ve said it before, and we’ll say it again: The Democratic path to survival in this very difficult midterm season for the party is through women. And that’s especially true after the Hobby Lobby decision. There’s no doubt Democrats are going to win women voters in the fall; the questions are by how much and whether it will be large enough to save the party’s Senate majority.

Todd, Murray and Dann also cite Dems’ favorable edge with Latinos as a big plus, while the GOP leans increasingly on stale whining about Obamacare, a dubious lawsuit fronted by an intemperate House Speaker and reduced to ugly immigrant-bashing, as the economy improves. This is not the political — or economic — landscape smarter Republicans wanted to see at midsummer.
Sure, there is plenty of time left for Dems to screw up, or the economy to falter. But right now, polls everywhere give the Republicans little to be encouraged about. The trendline at this juncture has an increasingly blue tint.