Vulnerable Senate incumbents are seeing an influx of cash as they build up their campaign bank accounts ahead of tough races in the 2018 midterm elections.

Senate Democrats in particular have kept up their high-dollar fundraising, with the party defending 10 seats in places that President Trump carried in November.

Meanwhile, Democratic challengers are also posting strong fundraising quarters that are on track with Republican incumbents’ figures. But GOP primary challengers looking to take on their party’s incumbents are still behind as they mount upstart challenges.

Here are five takeaways from Senate incumbents' and challengers’ third quarter fundraising reports:

Vulnerable incumbents still raking in millions

Vulnerable incumbents, particularly Democrats, are continuing to build on their significant fundraising hauls from previous quarters.

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Four vulnerable Senate Democrats topped $2 million, with 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-Mo.) leading the pack with $2.9 million raised in the third quarter. She raised the second-most of any Senate incumbent or candidate, trailing Sen. Elizabeth Warren Elizabeth WarrenJudd Gregg: The Kamala threat — the Californiaization of America GOP set to release controversial Biden report Biden's fiscal program: What is the likely market impact? MORE (D-Mass.) by less than $50,000.

Sen. 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) raised $2.6 million, while 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.) raised $2.4 million and Sen. 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 Jr. (D-Pa.) brought in $2.2 million.

While Florida Gov. Rick Scott (R) has yet to announce whether or not he’ll run for the upper chamber against Sen. 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.), Nelson still raised nearly $1.8 million. Sens. 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 (D-N.D.), Joe Donnelly Joseph (Joe) Simon DonnellyTrump meets with potential Supreme Court pick Amy Coney Barrett at White House Names to watch as Trump picks Ginsburg replacement on Supreme Court Momentum growing among Republicans for Supreme Court vote before Election Day MORE (D-Ind.) and 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-Mont.) each raised more than $1 million.

Vulnerable GOP incumbents are also raking in cash, even as they face primary challenges and tough general elections down the road. 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.) raised $1.17 million, while 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’s (R-Ariz.) raised $1.1 million, according to Washington Examiner.

Dem challengers outraising or keeping pace with GOP incumbents

Unseating an incumbent is always a tough feat, since they typically have fundraising advantages and better name recognition. But many Democratic challengers are keeping up with their incumbent GOP rivals.

Heller was narrowly outpaced by his likely Democratic opponent, Rep. Jacky Rosen (D-Nev.), who pulled in $1.19 million, according to Las Vegas Review-Journal. Heller still maintains a substantial cash on hand advantage of about $3 million.

Rep. Kyrsten Sinema (D-Ariz.), who is running to unseat Flake, raised $1.08 million, which was slightly behind the GOP senator’s haul. But Sinema has a larger balance, nearly $4.2 million compared with Flake’s $3.4 million.

While Texas isn’t seen as having a competitive race, Sen. Ted Cruz Rafael (Ted) Edward CruzThe Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy Murkowski: Supreme Court nominee should not be taken up before election Battle lines drawn on precedent in Supreme Court fight MORE’s (R-Texas) likely Democratic competitor is still raising money at a high clip. Cruz, who raised $1.76 million, outpaced Rep. Beto O’Rourke (D-Texas), but only by about $52,000. The Texas GOP senator still has a larger cash advantage with nearly $3 million more in his campaign account.

Alabama Dem sees influx of cash, lags in polls

Alabama’s Senate seat is expected to remain in GOP hands, but after former judge Roy Moore advanced out of the GOP runoff, Democrats are mulling whether they have a chance in the deep-red state.

Moore, who was suspended twice as a state Supreme Court chief justice, filed a pre-runoff fundraising report where he raised more than $960,000 between the end of July and early September. He ended with $285,000 in his campaign account on Sept. 6.

His Democratic opponent, Doug Jones, had low sums of money prior to the Democratic primary, but has seen a surge in donations as Democrats eye the seat. The former U.S. attorney raised more than $1.3 million from the end of July to the end of September. He has $1 million cash on hand.

Polls have shown Moore leading Jones by a single-digit margin, but a recent Fox News poll has been an outlier, with the two candidates tied.

Moore will have the chance to boost his fundraising with a Washington fundraiser in early November with headliners including Sens. Rand Paul Randal (Rand) Howard PaulSecond GOP senator to quarantine after exposure to coronavirus GOP senator to quarantine after coronavirus exposure The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill MORE (R-Ky.) and Mike Lee Michael (Mike) Shumway LeeMcConnell shores up GOP support for coronavirus package McConnell tries to unify GOP Davis: The Hall of Shame for GOP senators who remain silent on Donald Trump MORE (R-Utah), who recently endorsed him.

Fundraising gives candidates edge in crowded primaries

Primary season won’t start until next year, but fundraising could help elevate some candidates in crowded primaries.

In Indiana, GOP Rep. Luke Messer raised about $734,000, compared with GOP Rep. Todd Rokita, who raised about $433,000. Messer has a slight cash on hand advantage, but has a debt of about $93,000. This comes after Rokita outpaced Messer nearly 2-to-1 in the last fundraising quarter. Republican Mark Hurt is way behind with only $3,067 cash on hand.

In Montana, state auditor Matt Rosendale (R) raised more than $413,000, while businessman Troy Downing raised more than $311,000. Rosendale has the backing of Great America Alliance (GAA), the pro-Trump outside group with ties to former White House chief strategist Stephen Bannon. State Sen. Al Olszewski (R) was further behind with about $127,000. Retired Judge Russell Fagg announced this month and won’t need to file a fundraising report for the third quarter.

In West Virginia, GOP Rep. Evan Jenkins hauled in about $220,000, but it remains to be seen how much state Attorney General Patrick Morrisey (R) has raised. Morrisey could receive a bump now that he’s endorsed by GAA.

All GOP candidates are behind in fundraising compared with the Democratic senators they’re trying to unseat.

Insurgent candidates lagging in cash amid challenges to incumbents

Bannon has vowed to play in GOP primaries, which could give them an extra boost in trying to unseat incumbents. So far, these upstart candidates underperformed against the incumbents when it comes to fundraising.

In Arizona, former state Sen. Kelli Ward (R) raised just shy of $700,000 this quarter, a sizable uptick from her previous fundraising. But Ward, who unsuccessfully ran against Sen. John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (R-Ariz.) last year, ends September with less than $300,000 in her campaign account. That’ll be tough to compete with Flake in the primary or Sinema in the general election, each of whom has millions in their accounts.