Second-quarter fundraising reports are due next weekend, and candidates are likely to start announcing their totals in the days to come.

So who has the most to prove?

Below, we take a look at eight that have plenty at stake in their second-quarter reports (followed by what we think is a reasonable goal for each of them)...

* Sarah Steelman: The former Missouri state treasurer has led in every public poll of the GOP primary to face Sen. Claire McCaskill (D-Mo.), but she hasn’t raised much money and is at risk of being far outspent down the stretch. She needs to demonstrate at least a little fundraising life. (Goal: $500,000)

* Connie Mack: The Florida congressman is now the clear favorite to face Sen. Bill Nelson (D-Fla.) with former senator George LeMieux (R) dropping out. But questions remain about how formidable his campaign is, Nelson is raising big money, and this is an expensive state. (Goal: $1.2 million)

Rep. Joe Donnelly (D-Ind.) faces a crucial fundraising report, now that Sen. Richard Lugar (R-Ind.) lost his primary and Donnelly appears to have a chance against state Treasurer Richard Mourdock. (Joe Raymond — AP)

* Elizabeth Warren: Warren raised ungodly amounts of money in previous quarters (more than $12 million the last two) in Massachusetts, but she spent much of the second quarter trying to explain her past claim to Native American heritage. Did she suffer a drop-off thanks to the tempest? (Goal: $5 million)

* Charlie Summers: Republicans remain hopeful that a three-way race in Maine gives Summers a shot to beat popular former governor Angus King (I). But he raised just $69,000 in nearly two months before the primary, and it might be tough to raise money in a race that many are already writing off. (Goal: $250,000)

* Ted Cruz: He’s a tea party favorite in a GOP primary runoff with Lt. Gov. David Dewhurst, but he needs money to get it done in an expensive state and show that conservatives are rallying around him. Dewhurst has basically unlimited resources by virtue of self-funding; Cruz raised $530,000 in the first five-plus weeks of the quarter, before the primary. (Goal: $1.8 million)

* George Allen: The former senator has been outraised by significant amounts in each of the last four quarters, and it happened again in reports filed before the June primary, with former Democratic National Committee chairman Tim Kaine (D) edging him $1.1 million to $740,000. Now that Allen is the nominee, he needs to right he ship and gain parity. (Goal: $1.5 million)

* Tommy Thompson: The four-term former Wisconsin governor hasn’t raised money like a top-tier candidate — yet. A strong quarter would serve notice in the Aug. 14 primary that he remains the favorite, and it’s especially important with wealthy businessman Eric Hovde starting to contend. Hovde self-funded $1.5 million in the first quarter. (Goal: $1 million)

And now ... to the line!

10. New Mexico (Democratic-controlled): Environmental groups are chipping in big for Rep. Martin Heinrich (D-N.M.), helping him level an outside group playing field that generally favors the GOP. Former congresswoman Heather Wilson (R), meanwhile, recently said she will skip the Republican National Convention, which is probably a good move for her in this nominally blue state. (Previous ranking: 10)

9. Virginia (D): The Real Clear Politics average of polling in the open-seat race between Tim Kaine (D) and Allen has the race tied at 44 percent. That tells you all you need to know about a race that is widely expected to be among the closest and most expensive in the country. What will tip the scales either way? Is Kaine’s connection to President Obama a net neutral, negative or positive? (Previous ranking: 9)

8. Nevada (Republican-controlled): The last five public polls on this race have shown appointed Sen. Dean Heller (R) leading Rep. Shelley Berkley (D) by generally small margins. An NBC News/Marist College poll in late May showed Heller up two points even as Obama led Mitt Romney by the same margin. Keep in mind: This is one state where Romney may benefit from his Mormon faith due to a significant Mormon population; but a Washington Post report this week pointed to anecdotal evidence of crossover Romney-Berkley voters. (Previous ranking: 7)

7. Wisconsin (D): If current polling is to be believed, Republicans should really be rooting for Thompson in a contested GOP primary. A recent Marquette University poll showed him leading Rep. Tammy Baldwin (D) by eight points, but every other Republican either tied (former congressman Mark Neumann) or trailing by a significant margin (Hovde and state Assembly Speaker Jeff Fitzgerald). The same poll showed Thompson up 18 points in the primary, but a Hovde poll this week showed him within five points of the front-runner. (Previous ranking: 8)

6. Massachusetts (R): How close is this race? The last eight public polls in this race have shown Sen. Scott Brown (R-Mass.) and Warren within two points of each other. Warren appears to have finally put the whole Native American controversy behind her, but she still faces a popular incumbent who has been busy burnishing his everyman, middle-of-the-road reputation in the state, while she struggled to answer questions about her past. (Previous ranking: 6)

5. Montana (D): Neither Sen. Jon Tester (D) nor Rep. Denny Rehberg (R) is going to his party’s national convention, a testament to how close the margins are in this contest — and to the fact that neither man feels totally comfortable embracing his national party. Obama seems like more of a problem for Tester than Romney is for Rehberg, but in a race that is expected to be this close, neither of them are taking any chances. (Previous ranking: 5)

4. Missouri (D): The GOP primary here remains very jumbled. Steelman has been the nominal favorite for a while but can’t raise money (like any ... at all); businessman John Brunner has the most well-funded operation but lacks name ID; and Rep. Todd Akin this week got a boost from an ad featuring Mike Huckabee. Sen. Claire McCaskill (D) is still an underdog, but her fate depends plenty on how an undistinguished GOP field shakes out in the primary, which is now just one month away. Keep an eye on Brunner, in particular, who could be the GOP’s best hope. (Previous ranking: 4)

3. North Dakota (D): Democrat Heidi Heitkamp continues to impress here, turning what was once thought a shoo-in for Rep. Rick Berg (R) into a real race. But it’s still an uphill battle for any Democrat in this conservative state, and Republicans will use (and are using) every opportunity to tie Heitkamp to Obama and his health-care bill. (Previous ranking: 3)

2. Nebraska (D): State Sen. Deb Fischer (R) has emerged from a shocking primary upset as a heavy favorite against former senator Bob Kerrey (D). A survey conducted for her campaign in June gave her a massive 25-point lead, and other data suggests she has a solid double-digit edge. Kerrey’s problem is that, no matter what his past electoral record in the Cornhusker State looks like (and it’s quite good), he is running in one of the most Republican states in the country in a presidential year. (Previous ranking: 2)

1. Maine (R): Former governor Angus King, an independent, is still playing coy when asked which party he would caucus with in the Senate. But the total lack of support from the national Democratic Party for their nominee, Cynthia Dill, suggests Democrats have placed their bets. (Previous ranking: 1)

Chris Cillizza and Rachel Weiner contributed to this report.