You might not know it from the headlines, dear reader, but the presidential contest is not the only election happening in 2020. Control of the U.S. Senate is also up for grabs, and the party in charge of Congress’s upper chamber could determine the fate of many of the policies currently grabbing attention in the presidential campaign. As we noted right after the 2018 election, Republicans are favored to retain a majority in the Senate in 2020, but Democrats also have a realistic — if difficult — path to winning back control. This is the first of a series of regular updates on what’s happening in Senate contests around the country, so let’s take a look-see at the latest developments.

First, the top-line situation. Republicans are favored to hold on to the Senate, as they currently have a 53-to-47 seat edge, which means Democrats must gain a net of four seats for outright control, or three seats and the vice presidency, as the vice president casts the tiebreaking vote. What’s more, the competitive races in the Senate in 2020 will probably be on Republican-leaning turf, which should give the GOP a baseline advantage. However, Democrats’ silver lining is that the GOP has to defend 23 of the 35 seats on the ballot next year, and election forecasters Inside Elections, Sabato’s Crystal Ball and The Cook Political Report currently rate Democrats’ opportunities to pick up seats more favorably than Republicans’. (Though Republicans, of course, can win the Senate by simply hanging on to the seats they have.)

And keep in mind that the presidential race at the top of the ticket may be critical in determining which party wins control because of just how nationalized our elections have become. In the 2016 election, for instance, every state with a Senate race backed the same party for both president and Senate for the first time ever.

Republicans must defend nearly twice as many Senate seats Senators up for reelection in 2020, by their state’s partisan lean Incumbent Inc. Party State median Race Rating* Partisan Lean OPEN R WY Safe R R+47.4 Jim Risch R ID Safe R R+34.9 Jim Inhofe R OK Safe R R+33.9 Mike Rounds R SD Safe R R+30.6 Shelley Moore Capito R WV Safe R R+30.5 OPEN R TN Safe R R+28.1 Doug Jones D AL Lean R R+26.8 Tom Cotton R AR Safe R R+24.4 Ben Sasse R NE Safe R R+24.0 OPEN R KS Likely R R+23.3 Mitch McConnell R KY Likely R R+23.3 Steve Daines R MT Safe R R+17.7 Bill Cassidy R LA Safe R R+17.3 Lindsey Graham R SC Safe R R+17.2 John Cornyn R TX Likely R R+16.9 Cindy Hyde-Smith R MS Safe R R+15.4 Dan Sullivan R AK Safe R R+14.9 David Perdue R GA Likely R R+11.8 OPEN** R GA Likely R R+11.8 Martha McSally** R AZ Toss-up R+9.3 Joni Ernst R IA Lean R R+5.8 Thom Tillis R NC Toss-up R+5.1 Jeanne Shaheen D NH Likely D R+1.7 Mark Warner D VA Safe D D+0.1 Gary Peters D MI Lean D D+1.3 Cory Gardner R CO Toss-up D+1.5 Tina Smith D MN Likely D D+2.1 Susan Collins R ME Toss-up/Lean R D+4.9 OPEN D NM Likely D D+7.2 Jeff Merkley D OR Safe D D+8.7 Dick Durbin D IL Safe D D+13.0 Cory Booker D NJ Safe D D+13.3 Chris Coons D DE Safe D D+13.6 Jack Reed D RI Safe D D+25.7 Ed Markey D MA Safe D D+29.4 *Rating is the median rating among Inside Elections, Sabato’s Crystal Ball and The Cook Political Report. **Special election Open seats are ones with retiring or resigning senators. FiveThirtyEight’s partisan lean metric is the average difference between how a state votes and how the country votes overall, with 2016 presidential election results weighted at 50 percent, 2012 presidential election results weighted at 25 percent and results from elections for the state legislature weighted at 25 percent. Note that the partisan leans in this article were calculated before the 2018 elections; we haven’t calculated FiveThirtyEight partisan leans that incorporate the midterm results yet.

But declining approval ratings may be a warning sign for endangered Republican incumbents in battleground states. The partisan lean metric in the table above measures how much more Democratic- or Republican-leaning a state is than the country as a whole, and all five GOP senators defending seats in states with a partisan lean of less than R+10 saw their approval ratings worsen in the third quarter of 2019, according to data from Morning Consult. And all but one — Arizona Sen. Martha McSally — has a net negative rating (approval rating minus disapproval rating).

Five vulnerable GOP senators’ net approval has dropped Net approval rating (approval rating minus disapproval rating) in the second and third quarters of 2019 Net approval in 2019 Senator State 2nd QTR 3rd QTR Change Martha McSally AZ +2.9 +2.1 -0.8 Susan Collins ME -3.9 -5.8 -1.9 Cory Gardner CO +0.3 -2.9 -3.2 Thom Tillis NC -1.5 -5.1 -3.6 Joni Ernst IA +4.5 -4.0 -8.5 Source: Morning Consult

This is particularly worrisome for Sens. Susan Collins of Maine and Cory Gardner of Colorado, who will likely need some ticket-splitting in their Democratic-leaning states to win reelection. Most notably, Iowa Sen. Joni Ernst’s net approval rating dropped about 9 percentage points, falling into negative territory, though it dropped the most among Republican voters, who may come back into her fold by Election Day. Democrats probably need to defeat most or all of these senators — North Carolina Sen. Thom Tillis is the fifth — to capture the Senate, and they have to be pleased that the public image of these incumbents has taken a hit. Of the Democrats in currently competitive contests (that is, those not rated as “safe” for either party), only Minnesota Sen. Tina Smith saw a decline in her net approval, although it remains fairly positive overall (+13).

Yet it’s certainly not all bad news for Republicans. Recent polling in Michigan, for instance, suggests they have a real shot of putting the state’s Democratic-held seat in play. Two recent polls found Democratic Sen. Gary Peters barely ahead of or in a dead heat with Republican John James, who lost Michigan’s 2018 Senate race but performed better than expected relative to the Democratic lean of the national environment. Although another poll found Peters ahead by 16 points, so it’s not entirely clear yet how competitive this race is, but given that President Trump carried Michigan by 0.2 points in 2016, it should be a competitive environment where James could take down Peters, especially if he can once again outperform expectations.

But we’re a long way from November 2020, so plenty of curveballs could still shake up the Senate picture between now and then. Consider, for example, that former Attorney General Jeff Sessions is reportedly considering a run for his old seat, which Democratic Sen. Doug Jones won in a surprise victory over scandal-ridden Republican Roy Moore in a 2017 special election. Major contenders for the GOP nomination — including Moore, who’s running again — aren’t inclined to get out of Sessions’s way just yet though, as his position in the party is somewhat complicated given Trump’s still-simmering anger over Sessions’s decision to recuse himself from the investigation into Russian interference in the 2016 election. If Sessions runs and Trump openly opposes him, that might make for a wide-open and unpredictable GOP primary. Jones, who is an underdog for reelection, would probably prefer the chaos, but we’ll know more very soon — the deadline to enter the race is Nov. 8.

As in Alabama, the eventual nominees in a handful of other races could influence how competitive they are. For instance, although New Hampshire is very narrowly divided between the parties (Hillary Clinton carried the state by less than half a point in 2016), election forecasters think Democratic Sen. Jeanne Shaheen is in relatively good shape to win reelection — the median race rating there is “Likely Democratic.” That’s partly because the GOP lacks a top-tier challenger there, but that could change if a high-profile Republican like former Trump campaign manager Cory Lewandowski jumps into the race. New Hampshire Republicans have said they worry that Lewandowski could harm the GOP ticket, but considering the razor’s edge by which Trump lost New Hampshire in 2016, Lewandowski’s entrance into the race while Trump is at the top of the ticket could make the seat less safe for Democrats.

Meanwhile, Democrats are hoping that state Sen. Barbara Bollier, a Republican-turned-Democrat who is their likely nominee, can run a competitive race for Kansas’s open seat despite the state’s strong Republican lean (R+23.3). And the GOP candidate most likely to make that possible for Democrats is former Kansas Secretary of State Kris Kobach, who lost the state’s 2018 gubernatorial race. For that reason, national Republicans don’t want Kobach to win the GOP nomination, but thanks to the crowded GOP primary field, Kobach’s conservative base of support might be enough for him to win with only a plurality. The real Kansas wild card, of course, is Secretary of State Mike Pompeo, who has done nothing to tamp down speculation that he might seek the seat. Pompeo is a former representative from Kansas and his entry might clear the GOP field — he doesn’t have a potential anti-Trump problem like Sessions.

As for the newest Senate race on the 2020 calendar — Georgia’s special election — there’s also a fair amount of uncertainty there. Republican Sen. Johnny Isakson announced that he will resign at the end of 2019, but Republican Gov. Brian Kemp has yet to announce who he will appoint in Isakson’s place. Some notable Democrats have entered the contest for Georgia’s other Senate seat (that’s right, both seats are up), but so far only Matt Lieberman — son of former Connecticut Sen. Joe Lieberman — has announced a bid for the special election. Notably, Democratic Rep. Lucy McBath appeared to be preparing a run for Isakson’s seat, but decided to seek reelection to the House instead. Republicans are favored in both Georgia races, but Democrats will still want to have strong candidates contesting both seats in case the electoral environment is friendly enough to make Georgia a swing state. The close gubernatorial race between Kemp and Democrat Stacey Abrams in 2018 could portend a competitive presidential contest there, though Trump won the state by 5 points in 2016.

There will be many more twists and turns in the 2020 Senate race, so watch this space — we’ll be tracking all the ins and outs of the battle to control Congress’s upper chamber.