Why Democrats are looking good at the House and not the Senate.

The home stretch is finally upon us. We're less than 60 days out of the midterms, and while there is a couple of primaries on the calendar-New Hampshire on Tuesday and Rhode Island on Wednesday-the world is expected to alter the big picture. These parties have found themselves on an emotional roller coaster this year: Democrats lost a pair of 10-term congressional incumbents at the hands of progressive insurgents, while a convicted coal baron made a high-profile attempt to snatch another.

And yet, the overall state of play in the battle for control of congress remains largely unchanged since one year ago. The short version: Democrats are looking good in their bid to retake the House. Meanwhile, the position they find themselves in the Senate, to use a technical political science term, is meh.

A necessary epistemological caveat: Nothing is guaranteed. Historical precedents are important, but by definition they can only tell us what happened in the past. Likewise, polls are a snapshot of where stand today, not how they'll look tomorrow. We can use both of us to educate ourselves, but the political forecasting is an imperfect science, regardless of whether you're a number-cruncher like FiveThirtyEight's Nate Silver or a politics professor like the University of Virginia's Larry Sabato.

That said: Democrats will pick up seats in the House, though not necessarily the 23 they need to retake the chamber.

For starters, there's history. The party that does not control the presidency has won congressional seats in 35 out of the 38 midterms dating back to the end of the Civil War. And according to the Cook Political Report's count, there have been seven midterms elections since 1966 where a president's approval rating "hovered" below 50 percent-an, um, generous term for where Donald Trump sits at the moment-and in those, the opposite party at least two dozen House seats in all but one. The sole exception was in 2014 in the middle of Barack Obama's second term. The GOP won "only" 13 seats that year, in no small part because Democrats did not have that many after getting shellacked in the 2010 midterms.

The polls suggest that general trend will continue. Democrats are up to 7.8 points in RealClearPolitics Unweighted average of the generic ballot and ahead 8.5 points in FiveThirtyEight's weighted one, which ranks higher-rated pollsters. (Those margins were 8.1 and 9.3, respectively, on March 6, the day of the first midterm primary, and 8.6 points and 8.1 points this time last year.) But flipping House seats is not the same as flipping enough of them. And Democrats have their work cut out there. Thanks to gerrymandering, geography, and other factors, the GOP has a sizable built-in advantage in congressional races. Experts disagree on the true size of the cushion, but most think Democrats will need to win the national vote by somewhere between 4 and 11 percentage points to gain control of the House. As they are for most of the year, Democrats are currently splitting the difference.

But while Democrats' edge in the generic ballot has waxed and waned, nonpartisan handicappers have moved one race after another in their direction. Cook, for example, currently believes 66 GOP seats are in play, 28 more than it did in January. Over that time, the number of Democratic seats in play fell from seven to five.

In Pennsylvania, where the state Supreme Court redrew the congressional map this year, Democrats have a chance to pick up six seats, including in the new 17^th District, where the Democrats' special election hero Conor Lamb is up against Rep. Keith Rothfus. In North Carolina, where did the court run once again? It's too late to redraw an unconstitutionally gerrymandered map before November, Democrats nonetheless have a real shot at picking up three seats, including in the 9^th, where U.S. Rep. Robert Pittenger lost his primary GOP to Mark Harris, opening the door to Democrat Dan McCready. And in California, Trump lost two years ago-a list that does not include the 50^th, where GOP Rep. Duncan Hunter has been indicted for fraud and crime crimes. (Anyone wanting to keep tabs on these and other exciting midterm races should subscribe to Slate's Hot Seats newsletter.) With so many openings, Democrats have a variety of different paths to control the House.

And what about the Senate, where Democrats have to pick up just two seats to take control? If House Democrats appear to be gaining seats, why is not the case for their colleagues in the upper chamber? The first and foremost reason: a truly unforgiving midterm map.

Thanks to the quirks of the electoral calendar, in which roughly one of the members of the Democratic caucus faces re-election this fall-and-fall of 26 incumbents are running in states Trump won two years ago.
Meanwhile, Republicans are defending just nine of their 51 seats, only one of which is in a state Trump lost (Nevada).

Cook and other nonpartisan handicappers currently think GOP-held seats: Arizona, Tennessee, and Nevada are toss-ups, while Texas is within Beto O'Rourke's reach. If Democrats win two of those-a solid haul! -They'd still need each and every one of their own incumbents to survive. And if Democrats were to sweep all four-a-Texas-sized yew-Republicans would still be able to keep control of the chamber if they can knock off three-state Democrats, who are considered vulnerable. Democrats' margin for error in the Senate, then, is not just smaller than it is in the House-it is nearly nonexistent.