Vulnerable Senate Democrats on the ballot in 2018 continued their strong fundraising rate in the second quarter of 2017, according to early looks at figures released by their Senate campaigns.

Republicans see the upcoming midterm elections as a prime opportunity to expand their party’s majority in the Senate, thanks to a favorable set of races on the midterm ballot.

Democrats have to defend 10 seats won by President Trump in November, with five of those in states Trump won by at least 20 points. The GOP, on the other hand, has to defend just two tough seats in Arizona and Nevada.

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All Senate fundraising reports are due by Saturday. But early figures from the Senate campaigns show that vulnerable incumbents on both sides of the aisle are stockpiling some serious cash to defend their seats next year.

Missouri Sen. Claire McCaskill Claire Conner McCaskillMomentum growing among Republicans for Supreme Court vote before Election Day Democratic-linked group runs ads in Kansas GOP Senate primary Trump mocked for low attendance at rally MORE (D) raised the most of any vulnerable senator in the second fundraising quarter. Her campaign announced that she raised $3.1 million, bringing her total cash on hand to $5.1 million.

That isn’t the only piece of good news McCaskill received this month. Missouri Rep. Ann Wagner (R), one of the top likely candidates to take on McCaskill, announced last week that she would not seek a Senate bid.

Sens. Sherrod Brown Sherrod Campbell BrownBipartisan praise pours in after Ginsburg's death Emboldened Democrats haggle over 2021 agenda Hillicon Valley: Russia 'amplifying' concerns around mail-in voting to undermine election | Facebook and Twitter take steps to limit Trump remarks on voting | Facebook to block political ads ahead of election MORE (D-Ohio) and Bob Casey Robert (Bob) Patrick CaseySecond GOP senator to quarantine after exposure to coronavirus GAO report finds brokers offered false info on coverage for pre-existing conditions Catholic group launches .7M campaign against Biden targeting swing-state voters MORE (D-Pa.) tied for the second-highest totals among vulnerable Democratic members, both raising $2.6 million. Brown now has $6.7 million in the bank, while Casey has $5.5 million.

Sen. Tammy Baldwin Tammy Suzanne BaldwinKeep teachers in the classroom Cher raised million for Biden campaign at LGBTQ-themed fundraiser Democrats seek balance in backing protests, condemning violence MORE (D-Wis.) isn’t far behind, with $2.5 million raised over the past three months and $3.9 million in the bank. Following her are Sens. Bill Nelson Clarence (Bill) William NelsonDemocrats sound alarm on possible election chaos Trump, facing trouble in Florida, goes all in NASA names DC headquarters after agency's first Black female engineer Mary W. Jackson MORE (D-Fla.) and Debbie Stabenow Deborah (Debbie) Ann StabenowOVERNIGHT ENERGY: Trump rollbacks could add 1.8 billion tons of greenhouse gas emissions over 15 years: analysis | Intensifying natural disasters do little to move needle on climate efforts | Experts warn wildfire smoke could worsen COVID-19 GAO report finds brokers offered false info on coverage for pre-existing conditions Democrats back away from quick reversal of Trump tax cuts MORE (D-Mich.), who each raised $2.1 million. Nelson has $5.1 million on hand, while Stabenow has $5.8 million in the bank, according to the Detroit News.

Montana Sen. Jon Tester Jonathan (Jon) TesterPence seeks to boost Daines in critical Montana Senate race This World Suicide Prevention Day, let's recommit to protecting the lives of our veterans Filibuster fight looms if Democrats retake Senate MORE (D) raised $2 million and has $4.7 million banked away.

Rounding out the Democratic senators, Sen. Joe Donnelly Joseph (Joe) Simon DonnellyMomentum growing among Republicans for Supreme Court vote before Election Day Barrett seen as a front-runner for Trump Supreme Court pick Ex-Sen. Joe Donnelly endorses Biden MORE (Ind.) raised $1.5 million with $3.7 million on hand, while Sen. Joe Manchin Joseph (Joe) ManchinMomentum growing among Republicans for Supreme Court vote before Election Day Gardner on court vacancy: Country needs to mourn Ginsburg 'before the politics begin' Barrett seen as a front-runner for Trump Supreme Court pick MORE (W.Va.) raised $1.4 million with $3.5 million on hand and Sen. Heidi Heitkamp Mary (Heidi) Kathryn HeitkampCentrists, progressives rally around Harris pick for VP 70 former senators propose bipartisan caucus for incumbents Susan Collins set to play pivotal role in impeachment drama MORE (N.D.) raised $1.3 million.

Heitkamp, who still has not confirmed whether she’ll run for another term, has $3 million in the bank.

The strong numbers are good news for Democrats, as many of the incumbents will be facing tough reelection battles.

There are far fewer vulnerable GOP incumbents on the ballot.

Sen. Dean Heller Dean Arthur HellerOn The Trail: Democrats plan to hammer Trump on Social Security, Medicare Lobbying World Democrats spend big to put Senate in play MORE (R-Nev.), seen by most analysts as the most vulnerable GOP senator up for reelection, raised $1.4 million in the second quarter to bring him to $3.5 million in the bank, according to the Las Vegas Review Journal. While Heller’s fundraising figure stands at the bottom of the pack for the vulnerable incumbents, the steady fundraising and strong war chest could help ward off any potential primary opponents.

He’s drawn at least one Democratic opponent — Rep. Jacky Rosen (Nev.), who hasn’t yet announced her fundraising. Frequent candidate Danny Tarkanian is mulling a primary challenge to the right of Heller.

Arizona Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE, the other vulnerable Republican incumbent, raised $1.5 million and has $3 million in the bank. Despite being one of the few seats where Democrats can challenge an incumbent, top Democratic recruits remain on the sidelines.

Most of the candidates looking to challenge these incumbents had not yet released their fundraising hauls, as they have until the weekend to finalize their results. Since Senate candidate disclosures are filed on paper and need to be scanned into the online system, it could be days after the deadline before the entire snapshot is clear.

In a crowded GOP field for candidates looking to face Casey in Pennsylvania, real estate executive Jeff Bartos reportedly raised $1 million. Most of the Republican candidates have yet to post their fundraising numbers, but this puts Bartos miles ahead of state Rep. Rick Saccone, who raised only $15,000 and has $30,000 on hand.

At least half a dozen Republicans have filed to unseat Casey, with the potential for more challengers to announce in the coming months. Rep. Mike Kelly (R-Pa.), who’s weighing a Senate run, raised $370,000 and has $1.1 million cash on hand.

Lena Epstein, who was co-chair of Trump’s campaign in Michigan, brought in $460,000 since announcing her Senate bid against Stabenow in late May. She has more than $455,000 cash on hand. Epstein’s primary foe, former state Supreme Court Justice Bob Young, hasn’t released his numbers either.

In Indiana, GOP Rep. Todd Rokita, who has publicly toyed with a bid, raised $1 million in the second quarter to bring his cash on hand to $2.3 million. Rokita hasn’t announced a decision on whether he’ll jump in, but the big quarter could send a message to fellow GOP Rep. Luke Messer, who is also considering a bid. A source close to Messer told The Hill he's expecting to report around $600,000 raised this past quarter.

And in deep red Texas, Democratic Rep. Beto O’Rourke made a big splash, raising $2.1 million to take on Sen. Ted Cruz Rafael (Ted) Edward CruzVideo of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Democrat on Graham video urging people to 'use my words against me': 'Done' MORE (R). That's an impressive haul, but he faces a steep climb against Cruz — no Democratic politician has won statewide since 1994.

--This post was updated on July 14.