Washington (CNN)Tuesday's contests in Indiana, Ohio, North Carolina and West Virginia will kick off an active stretch of the primary season following an April hiatus.
Four big 2018 questions that will be answered over the next four weeks
By the end of the first week of June, 15 statewide primaries will have come and gone. Runoff races in Texas will also occur in that time.
The outcomes in these races will begin to provide answers to some key questions that will determine how November's midterm elections are shaping up in the House and Senate for both parties.
Thanks to a favorable map, Republicans have a chance to not only keep their Senate majority, but possibly expand it. Some in the party, however, fear that nominating Don Blankenship to run against Democratic Sen. Joe Manchin could cost the GOP a top pickup opportunity.
Defeating Manchin, the state's senior senator and former governor, was never going to be an easy task for Republicans regardless of which candidate emerged from the GOP primary between Blankenship, Rep. Evan Jenkins and state Attorney General Patrick Morrisey.
A Manchin-Blankenship contest, however, could pose an added challenge for the GOP in a state that Donald Trump carried by more than 40 points.
Blankenship, a former coal baron, spent a year in prison after being convicted of conspiracy to violate mine health and safety standards following a 2010 mine explosion that killed 29 workers. He has also compared Mitch McConnell to the Russians and unleashed a television ad ratcheting up his racially charged attacks on the Senate majority leader.
Democrats must defend 10 Senate seats in states Trump won in 2016, so every little advantage the party can get would be welcome news to them. For Manchin, a race against Blankenship is a potential game changer, but not one he could take for granted given West Virginia's conservative tilt.
In contrast to West Virginia, there isn't much concern about the outcome in Indiana, where Republicans believe any of the three candidates running -- Reps. Luke Messer and Todd Rokita, as well as former state Rep. Mike Braun -- give them a shot at defeating Democratic Sen. Joe Donnelly. The concern here is whether the bruising primary has already left the eventual nominee hobbled entering the general election contest against Donnelly. The good news is the early primary date leaves plenty of time for the Republican winner to recover -- and Trump is scheduled to hold a campaign rally in the Hoosier State on Thursday that could help to unify the party and shift the focus to Donnelly.
In Ohio, meanwhile, four-term Rep. Jim Renacci appears to be the favorite to claim the GOP Senate nod over businessman Mike Gibbons. A closer-than-expected victory though could spark questions about Renacci's ability to unseat two-term Democratic Sen. Sherrod Brown in the fall.
Republicans also have a contested Senate primary in Montana, with four candidates looking to challenge Democratic Sen. Jon Tester in a state Trump carried by 20 points. The frontrunner in the June 5 contest appears to be State Auditor Matt Rosendale, who has been endorsed by conservative Sens. Rand Paul, Ted Cruz and Mike Lee, as well as the Club for Growth's political arm, which is running ads on his behalf. Rosendale shares a similar flat top-style hair cut as Tester, but his Maryland roots have come under fire from former judge Russ Fagg. That line of attack could be something Tester, a native son of the Treasure State, grabs hold of in a general election battle.
Another competitive House special election is on the horizon in Ohio's 12th Congressional District -- the third such contest of 2018 and the seventh Democrat-versus-Republican House special since Trump took office.
Democrats so far have only been able to notch one victory -- Conor Lamb in Pennsylvania's 18th District -- but overperformance by Democratic candidates has signaled the party has a strong energy advantage this cycle.
Lamb eked out a single-digit win a district Trump carried by 20 points. In Arizona last month, Democrat Hiral Tipirneni lost by less than five points in a district the President won by 21 points.
Tuesday's primaries in the 12th District will determine who will represent each party in what could be another expensive race that will draw outsized attention and offer another clue for what might happen in November.
The battle on the Republican side reflects the divide between the establishment and grassroots wings of the party. State Sen. Troy Balderson is the candidate favored by mainstream Republicans, including former 12th District Rep. Pat Tiberi. Liberty Township Trustee Melanie Leneghan, a self-described "Trump conservative," is the choice of House Freedom Caucus co-founder Jim Jordan, who represents Ohio's 4th District.
Some Republicans worry Leneghan's brand of conservatism could turn off moderate voters in a district with some northern Columbus suburbs that went for Trump by 11 points.
The leading contenders on the Democratic side appear to be Franklin County Recorder Danny O'Connor, former Franklin County Sheriff Zach Scott and farmer John Russell, who is running on a progressive platform of single-payer healthcare and refusing to accept corporate donations.
The match-up in the August special election will help determine how good Democrats feel about their chances of winning this race. However Tuesday's primaries shake out, the results this summer will be examined for what they portend this fall.
The answer to this question will be watched not just for 2018 ramifications, but for 2020 as potential challengers to President Trump try to strike a balance between energizing the party's base and highlighting their electability for a general election audience.
The May 22 runoff in the Texas 7th Congressional District will give Democrats a sense of how much risk there is in getting involved in primary fights.
The Democratic Congressional Campaign Committee stirred controversy when it dropped opposition research on one of the party's candidates -- Laura Moser -- ahead of the March Democratic primary. Despite the DCCC's efforts, Moser advanced to the runoff against Houston attorney Lizzie Pannill Fletcher.
The attack included highlighting a 2014 Washingtonian piece by Moser in which the activist and author wrote she would "sooner have my teeth pulled out without anesthesia" than live in Paris, Texas. The committee feared the article could be turned into a general election attack ad by Republicans and jeopardize the party's prospects at flipping the seat, currently held by Rep. John Culberson, in a district Clinton narrowly won in 2016.
The move aggravated tensions within the Democratic Party between the progressive and establishment wings, with leaders such as Democratic National Committee Chair Tom Perez and Vermont Sen. Bernie Sanders criticizing the DCCC's approach.
Democrats may want to play in other primaries this cycle where they are concerned about nominating a candidate who could struggle to win a competitive race in a GOP-held district or where they might fail to place a candidate on the ballot at all (see the California section below). A Fletcher win in Texas might alleviate some concerns about doing so if the party believes it could help clear their path to the House majority.
For Democrats, the road back to the House majority is likely to run through California. The state is home to seven Republican-held districts that Hillary Clinton won in 2016 that Democrats are hoping to contest in 2018.
The danger for the party is that it could potentially be shut out of the general election in a few of these races, costing them an opportunity at flipping some very winnable seats. In California's top-two primary system, the two highest vote-getters, regardless of party, face off against each other in the general election.
The enthusiasm on the Democratic side this cycle has resulted in a flood of candidates running for office. Those crowded fields could fracture the Democratic vote enough to prevent one of the party's candidates from placing first or second in the primary.
The DCCC recently intervened in the race for California's 39th District, where GOP Rep. Ed Royce is retiring, adding lottery winner and Navy veteran Gil Cisneros to the committee's Red to Blue program. The party is hoping the move will give Cisneros a boost over the other Democrats in the race, including businessman Andy Thorburn, pediatrician Mai Khanh Tran, former Obama administration official Sam Jammal and others.
In California's 48th District, where GOP Rep. Dana Rohrabacher is seeking re-election, there are eight Democrats on the ballot. Three Democrats have dropped out, but did so too late to remove their names from the ballot. The leading contenders are neuroscientist Hans Keirstead and tech entrepreneur Harley Rouda. The field is complicated by the bid from former Orange County GOP chairman Scott Baugh, who is attacking Rohrabacher over his Russia ties and marijuana advocacy.
There is another crowded race in California's 49th District, where four Democrats and eight Republicans are running to replace retiring GOP Rep. Darrell Issa, who narrowly won re-election in 2016 in a district Clinton carried by seven points.
Two other races where overcrowding could become a factor are California's 10th District, where six Democrats and one Republican are running to challenge incumbent GOP Rep. Jeff Denham in a district Clinton won by three points; and, California's 50th District, where three Democrats and two Republicans are running to unseat scandal-plagued GOP Rep. Duncan Hunter.
Democrats need a net gain of 23 seats to retake the House majority. Failing to land candidates in competitive races like the 39th, 48th or 49th districts in California would leave the party looking for pickup opportunities elsewhere -- likely at seats that are less favorable to Democrats than those in the Golden State.