Big news in the Kentucky Senate race: after two polls showed challenger Alison Lundergan Grimes actually leading, Cook Political Report’s Jennifer Duffy now says that Senate Minority Leader Mitch McConnell’s re-election campaign is a “toss up.” Along with a solid Democratic recruitment in Georgia, Democrats can breath a little easier after what had been a long string of good news for the GOP.

Overall, then, here’s the quick update on the 2014 Senate cycle. Republicans are heavily favored to gain seats. They have a real chance to win a majority in the Senate. But a Republican majority still requires almost everything to go right for the GOP. Nate Silver, writing a couple of weeks ago, placed the chances that Republicans will take back the Senate at almost 50/50. At this point, I think that’s a little too optimistic for the GOP.

Assuming that Democrats retake what used to be Frank Lautenberg’s New Jersey Senate seat this fall — and that looks extremely likely — Democrats head into 2014 with a 55-45 majority and the vice-presidency, meaning that Republicans will need a net six seat gain. That’s a tall order. Here’s the rundown:

* Excellent Republican opportunities: Three Democratic retirements in which Republicans have recruited well and Democrats haven’t are the core of the GOP case for big gains. In West Virginia, South Dakota, and Montana — all Republican states for the presidency, but all states where Democrats can be competitive in other races — Republicans have put up a strong candidate while Democrats have little or nothing. Charlie Cook right now rates South Dakota as Likely Republican, and the other two Lean Republican. That’s three seats likely going to the GOP.

* Good Republican opportunities: Four Democratic incumbents are running in good Republican states: Mark Begich in Alaska, Mary Landrieu in Louisiana, Mark Pryor in Arkansas, and Kay Hagan in North Carolina. It’s not clear yet how strong their opponents will be, although all four should draw at least one challenger who could win if things go right.

* Possible (but unlikely) Republican opportunities: Democratic retirements in Iowa and Michigan give Republicans some hope in marginal Democratic seats. But so far Democrats have found strong candidates while Republicans have not. In Minnesota, first-term Senator Al Franken was assumed potentially vulnerable after squeaking out a very narrow victory in 2008, but he seems to have solidified his position — and Republicans, so far, haven’t found any takers to challenge him.

That makes seven real targets for Republicans at this point: three very good chances for takeovers, and four very plausible ones. They would need six of seven to win. Possible? Sure. Likely? Hard to say. But what makes it tougher is what’s changed in the last few weeks:

Good Democratic opportunities: A Republican retirement in Georgia has yielded a very messy-looking primary, with a good chance that they’ll nominate a relatively weak Tea Party candidate. That could still produce a Republican win, but Democrats have countered with Michelle Nunn, daughter of the long-time Democratic Senator. And in Kentucky, Senate Minority Leader Mitch McConnell is running into all kinds of trouble. Not only is Democratic challenger Grimes already polling extremely well but McConnell also has a Tea Party primary challenger to worry about.

Bottom line: Republicans will have to net six seats, which will probably mean either knocking off three Democratic incumbents (if Republicans hold Georgia and Kentucky) or, harder, knocking off four Democratic incumbents (if Republicans lose either Georgia or Kentucky).

One major caveat, however. It’s still early enough that significant changes could happen. Republicans could still find a strong candidate in Minnesota, Iowa, or Michigan. Or: a seemingly strong Republican candidate in any of their seven strong opportunities could still wind up losing a primary to this cycle’s version of Todd Akin or Christine O’Donnell. Or: these are politicians; you never know when a perfectly strong incumbent will suddenly hit a scandal. Or: unexpected late retirements (say Susan Collins, which would move Maine into the Likely Dem column) could still change the map.

In other words, right now it appears that Democrats will hold somewhere between, say, 48 and 54 seats in the next Senate…but it’s still early enough that even that wide range could wind up missing some important developments. And we still have no idea whether Barack Obama will be popular or unpopular in 2014, or how much (if any) damage Republicans will do to themselves in the budget showdown this fall, in continued debate on immigration, and in whatever other craziness their Gohmert bran drags them into. Nor can we account or any major events — with the economy, foreign affairs, or anything else — that could affect single elections or the entire election cycle.

We do, however, have a pretty good “unless something happens” map of the election cycle. And for that, there is a Republican path to 51, but as of now it’s a very narrow one. It is likely that Republicans will leave one or more pickup opportunity on the table. Which means, for now, that Dems are very likely to have a bad election and lose seats, but they are also narrowly favored to hold their majority.