Eight Democrats have topped $1 million raised in the last three months. Sen. Al FrankenAl FrankenFranken emerges as liberal force in hearings Trump nominees dodge 'climate denier' charge Justice requires higher standard than Sessions MORE (Minn.) leads the pack so far with just under $2 million raised, with Sen. Mark PryorMark PryorCotton pitches anti-Democrat message to SC delegation Ex-Sen. Kay Hagan joins lobby firm Top Democrats are no advocates for DC statehood MORE (Ark.) close behind after a $1.9 million quarter. Sen. Kay HaganKay Hagan Former Sen. Kay Hagan in ICU after being rushed to hospital GOP senator floats retiring over gridlock 2016’s battle for the Senate: A shifting map MORE (N.C.) brought in $1.6 million, Sen. Mark UdallMark UdallLive coverage: Tillerson's hearing for State The rise and possible fall of the ‘Card’ in politics Gardner's chief of staff tapped for Senate GOP campaign director MORE (Colo.) raised $1.5 million, and Sens. Mary LandrieuMary LandrieuFive unanswered questions after Trump's upset victory Pavlich: O’Keefe a true journalist Trump’s implosion could cost GOP in Louisiana Senate race MORE (La.) and Jeanne Shaheen Jeanne ShaheenThe Hill's 12:30 Report Trump reinstates ban on US funds promoting abortion overseas Trump poised to reinstate 'global gag rule' on Roe v. Wade anniversary: report MORE (N.H.) brought in $1.2 million apiece. Landrieu has just shy of $3.5 million in the bank for her reelection push.

Early money is key for these candidates, as many are likely to face well-funded challengers and Republican-affiliated outside groups have a big cash advantage. Candidates also get air time at cheaper rates than committees and outside groups, making their money go further. 

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One caveat: Sens. Max BaucusMax BaucusFive reasons why Tillerson is likely to get through Business groups express support for Branstad nomination The mysterious sealed opioid report fuels speculation MORE (D-Mont.) and Mark BegichMark BegichThe future of the Arctic 2016’s battle for the Senate: A shifting map Trump campaign left out of Alaska voter guide MORE (D-Alaska) haven't posted their fundraising totals, and candidates with lower numbers often wait until the last minute to put their numbers out. Baucus already has $3.6 million in the bank, however, money that goes far in the inexpensive state. Begich had just shy of $1 million as of the end of 2012.

Another solid haul comes from Rep. Bruce BraleyBruce BraleyTrump: Ernst wanted 'more seasoning' before entertaining VP offer Criminal sentencing bill tests McConnell-Grassley relationship Trump's VP list shrinks MORE (Iowa), Democrats' likely nominee to replace retiring Sen. Tom HarkinTom HarkinGrassley challenger no stranger to defying odds Clinton ally stands between Sanders and chairmanship dream Do candidates care about our health or just how much it costs? MORE (D-Iowa). Braley brought in $1 million as well.

In most of these races there are no announced GOP candidates, giving Democrats a jump-start on fundraising. Rep. Shelley Moore CapitoShelley Moore CapitoGOP senators: Give states the option of keeping ObamaCare Five takeaways from Pruitt's EPA hearing Last Congress far from ‘do-nothing’ MORE (W.Va.), the GOP front-runner to replace retiring Sen. Jay RockefellerJay RockefellerObama to preserve torture report in presidential papers Lobbying world Overnight Tech: Senators place holds on FCC commissioner MORE (D-W.Va.) did have a strong haul for an inexpensive state, bringing in more than $900,000. Rep. Bill Cassidy (R-La.), who recently announced a bid against Landrieu, brought in $500,000 but has a strong $2.4 million warchest.

Pryor, Landrieu, Hagan, Begich and Baucus are likely the most vulnerable incumbents.