Ahh, flowering trees, brilliant sunshine, abundant campaign ads, lawn signs poking out of the bright green grass. Primary season has sprung, and it’s coming to a state near you. This week’s contests are in Idaho, Nebraska, Oregon and Pennsylvania, and there are several races you should care about.

Some quick housekeeping: Throughout this preview, we’ll indicate the competitiveness of each state and district using a metric we call partisan lean, which is calculated from the past two presidential election results within its boundaries. Partisan lean is a representation of how much more Democratic or Republican an area is than the nation as a whole. For example, a district with an R+7 partisan lean would be expected to vote Republican by 7 percentage points in a neutral national environment — or deadlock in the event Democrats win the national popular vote by 7 points. But we’re getting ahead of ourselves; first the parties need to nominate their candidates.

Pennsylvania

Races to watch: 1st, 5th, 7th, 10th and 14th congressional districts; governor

Polls close: 8 p.m. Eastern

When the Pennsylvania Supreme Court struck down Pennsylvania’s Republican-drawn congressional map and imposed one much friendlier to Democrats, it was like hitting reset on all of the state’s U.S. House races. Incumbents gained hordes of new constituents to introduce themselves to; challengers had to reconsider where to run. Partly as a result of the new map, seven of Pennsylvania’s 18 congressional districts have no incumbent running in them in 2018. That’s led to 21 contested congressional primaries — the most since 1984 — featuring 84 candidates.

In the 1st Congressional District, Democrats will probably choose either former Navy prosecutor Rachel Reddick or philanthropist Scott Wallace to face GOP Rep. Brian Fitzpatrick. Wallace espouses the same brand of progressive politics as his grandfather Henry Wallace, Franklin D. Roosevelt’s vice president, and has pumped $2.5 million of his own money into his campaign. The race has been negative: Wallace has attacked Reddick for being a Republican for most of her life, while Reddick’s ads tag Wallace as a carpetbagging “Maryland multimillionaire.” This is a swing district, with an R+1 partisan lean, so Reddick may be Democrats’ safest bet for the fall, although it’s hardly so red that Wallace can’t win.

No fewer than 10 Democrats are running for the 5th District, former Republican Rep. Pat Meehan’s redrawn seat. The 5th is 26 points more Democratic-leaning than the country at large — hence the crowded field (whoever wins the Democratic primary has a great chance of winning the general election over the sole Republican candidate, Pearl Kim). But such a large field makes for an unpredictable race; 20 percent of the vote may be enough to win. Take them for what they’re worth — perhaps not much — but three Democratic-conducted polls have been released, all saying that attorney Mary Gay Scanlon leads and state Rep. Greg Vitali is in second. Two other candidates, former federal prosecutor Ashley Lunkenheimer and former Philadelphia Deputy Mayor Rich Lazer, have been the beneficiaries of super PAC spending and can’t be counted out.

There aren’t many Democrats like John Morganelli running for Congress in 2018. The longtime Northampton County district attorney opposes abortion, vilifies “illegal aliens” and sought a job in the Trump administration. Still, he’s arguably the front-runner in the 7th District Democratic primary. Plenty of Democrats would prefer someone more liberal — the problem is that they can’t agree on whom. Emily’s List is backing Allentown City Solicitor Susan Wild, while Bernie Sanders has stumped for pastor Greg Edwards, who has also raised the most cash. Some observers believe Morganelli would help Democrats win back working-class voters in this evenly split (D+0.04) district, but the 7th District is a bit like the 1st: It’s swingy enough that a more conservative Democratic nominee might have an advantage, but it’s not red enough that a liberal nominee would be at much of a handicap (especially in a Democratic-leaning environment). Republicans, meanwhile, will choose between Marty Nothstein, who won an Olympic gold medal in cycling in 2000, and former Lehigh County Commissioner Dean Browning.

In a high Democratic wave, Republican Rep. Scott Perry could be swept away in his R+11 10th District, but it’s not clear who the strongest Democratic contender would be. Former Senate and White House staffer Shavonnia Corbin-Johnson unexpectedly posted the district’s best fundraising haul in the first quarter of 2018; she also recently earned the endorsement of Emily’s List. Other Democrats in the running include former Army Lt. Col. George Scott and public health scientist Eric Ding.

Finally, in the 14th District, state Sen. Guy Reschenthaler faces state Rep. Rick Saccone for the GOP nomination. Saccone, of course, became persona non grata in the Republican Party after losing an eminently winnable March special election to Democrat Conor Lamb, but Reschenthaler has come under fire too: He wrote an effusive foreword for a book that contained anti-gay and racist language, calling it “commonsense” and “what we all wanted to say.” Those flaws and March’s shocker notwithstanding, either Republican should be able to hold this now-even-redder (R+29) seat in the fall.

These aren’t the only Keystone State districts worth your time, but my editor does give me word counts for these things. The truly dedicated might also pay attention to the Democratic primary in the 4th and the Republican primaries in the 9th and 13th. In addition, three districts likely to be targeted in the fall will not see competitive primaries tonight: the Republican-held 6th and 17th Districts (D+5 and R+6, respectively) and the Democratic-held 8th (R+7).

In statewide races, Rep. Lou Barletta is expected to sweep aside state Rep. Jim Christiana in the Republican primary for U.S. Senate. Even though Pennsylvania is 2 points to the right of the rest of the country, incumbent Sen. Bob Casey is one of the less vulnerable vulnerable Democrats in the Senate, which is unlikely to change no matter who wins the Republican nomination.

At last, one of the nastiest primaries in the country has unfolded on the Republican side for Pennsylvania governor. State Sen. Scott Wagner, the owner of a waste-management company, and health care consultant Paul Mango have both plowed millions into their own campaigns, using an onslaught of TV ads to muscle their way to the front of the pack. In recent weeks, they’ve gone nuclear on one another: Mango aired an ad so savage that the state GOP (which formally endorsed Wagner) called on it to be taken down. When Mango refused, Wagner issued a withering response ad starring his daughter. (Sample quote: “Paul Mango, you’re not half the man my father is.”) A third candidate, attorney Laura Ellsworth, is hoping to pull a Mike Braun and capture a plurality on the strength of voters turned off by the negativity. The latest survey of the race, from Susquehanna Polling and Research, does show her closing, but she still sits in third place (18 percent) behind Wagner (37 percent) and Mango (23 percent).

Polls of the general election have concurred that Wagner would come the closest to beating Gov. Tom Wolf, but the Democratic incumbent would still start out with a healthy edge; perhaps the vicious primary has already taken its toll.

Nebraska

Races to watch: 2nd Congressional District

Polls close: 9 p.m. Eastern

Lincoln City Councilwoman Jane Raybould is very likely to be the Democratic nominee against Republican Sen. Deb Fischer. And state Sen. Bob Krist is the only candidate with serious money and experience in the Democratic primary for the right to face GOP Gov. Pete Ricketts. (Both Republicans are heavily favored in this R+27 state.) That leaves Nebraska’s 2nd Congressional District as by far the most interesting race in the Cornhusker State.

Although the district has a partisan lean of R+6, Republican incumbent Don Bacon won it in 2016 by just 1 percentage point over then-Rep. Brad Ashford. Nancy Pelosi and the DCCC both want Ashford to be their standard-bearer once again, and with $571,000 raised, he looks like the favorite. But nonprofit executive Kara Eastman has collected a respectable $356,000 and has campaigned as an unapologetic member of the anti-Trump #Resistance. While Ashford has sung the virtues of compromise and adopted middle-of-the-road positions, Eastman has pledged to fight for liberal priorities like single-payer health care. If there’s one race that epitomizes the Democratic divide between pragmatism and progressivism, it’s this one — and in a reddish toss-up district, the stakes are high.

Idaho

Races to watch: governor

Polls close: 10 p.m. Eastern in the southern half of the state, 11 p.m. Eastern in the north

There are three front-runners in the GOP primary for governor, and each represents a different wing of the party. Mild-mannered Lt. Gov. Brad Little, whom outgoing Gov. Butch Otter has endorsed, touts his inside knowledge of government workings. Wealthy developer Tommy Ahlquist occupies the “outsider businessman” lane; nearly $2 million of his own money has made him by far the race’s biggest spender. And U.S. Rep. Raul Labrador is running as the fiery conservative: He is a co-founder of the House Freedom Caucus and boasts that he is so close with Trump that he interviewed for a Cabinet position.

The campaign has been mean-spirited, with Ahlquist in particular taking heat for writing in Marco Rubio instead of voting for Trump in the 2016 general election and donating to his potential Democratic opponent in 2014. The outcome of the primary shouldn’t change the consensus that Republicans are very likely to retain this governorship, but it may have major policy implications. Idahoans are expected to vote on a ballot measure to expand Medicaid this fall, and Labrador has said that he would consider overturning the initiative if it were to pass.

In the Democratic primary, businessman A.J. Balukoff, the party’s 2014 gubernatorial nominee, has spent six times as much money as state Rep. Paulette Jordan, who would be Idaho’s first female governor and the first female Native American governor in the country. Jordan has drawn the endorsement of Planned Parenthood, Democracy for America and other national progressive groups, but Idaho Democratic politicians are largely in Balukoff’s corner, an acknowledgment that he is a better fit for this conservative (R+34) state.

Oregon

Races to watch: governor

Ballots due: 10 p.m. Eastern in part of Malheur County, 11 p.m. Eastern everywhere else

Oregon is 9 points more Democratic than the nation as a whole, and the state has had only Democratic governors since the mid-1980s. But in the past, moderate Republicans have ridden the overwhelming financial backing of Oregon’s business community (Oregon has no campaign contribution limits) to within just a few percentage points of Mahonia Hall.

State Rep. Knute Buehler is trying to chart that same course against incumbent Democrat Kate Brown in 2018, but he has hit an unexpected speedbump in primary challengers Sam Carpenter, a consultant whose slogan is “Make Oregon Great Again,” and Greg Wooldridge, a former Navy pilot. The staunchly conservative duo have criticized Buehler for his many centrist positions, such as support (with some exceptions) for legal abortion, sanctuary cities and gun control. Buehler has felt threatened enough that he is blanketing the state with ads that accuse Carpenter of not paying his taxes; Buehler poured twice as much money into broadcast advertising in April alone as his opponents have spent, combined, in the entire campaign. An internal poll for Carpenter’s campaign claimed that Buehler led Carpenter 39 percent to 24 percent, with Wooldridge at 12 percent, suggesting that the media blitz was working. (Again, though, internal polls are highly suspect — Carpenter released the poll to argue that the anti-abortion vote was being split and that Wooldridge should drop out.) Most likely, however, only Buehler has the crossover appeal to put a scare into Brown in the fall.