Now that the third quarter has ended, a fresh round of Senate fundraising reports will be released over the next couple of weeks, with keen interest on vulnerable incumbents who posted strong hauls during the first six months of the year, including Sens. Mark Begich, D-Alaska, and Mark Pryor, D-Ark., and Senate Minority Leader Mitch McConnell of Kentucky.

With more challengers having launched Senate bids over the summer, the fresh figures due to the Federal Election Commission by Oct. 15 will show which hopefuls are off to a hot start and are giving incumbents a run for their money.

Here are our top five Senate fundraising reports to watch.

1 Any McConnell challenger

McConnell posted $9.6 million in cash on hand at the end of June — tops in the Senate — before either of his top two challengers had entered the race. Now that Kentucky Secretary of State Alison Lundergan Grimes, a Democrat, and Louisville businessman Matt Bevin, a Republican, have launched challenges, they’ll have to show how much excitement their bids have garnered so far.

The potential to oust McConnell no doubt serves as a fundraising boon for his challengers. Even with all the outside money already flowing into the state, both contenders will be looking to cut into McConnell’s head start to give them a realistic chance for victory next year.

2 Rep. Colleen Hanabusa, D-Hawaii

This may be the only race in the country where the incumbent — appointed Sen. Brian Schatz —isn’t a solid favorite to win his party’s nomination. In office since late December, Schatz outraised the second-term Hanabusa by $400,000 in the second quarter.

Hanabusa formally announced her campaign in early May, so this was her first full reporting quarter as a Senate candidate. As the incumbent, Schatz has the fundraising resources of the Democratic Senatorial Campaign Committee at his disposal, while Hanabusa has the backing of EMILY’s List.

3 North Carolina Speaker Thom Tillis, Republican

The announcement by state Senate President Phil Berger last week that he would not run for Senate in North Carolina left Tillis as the leading GOP contender to take on the first-term Hagan. But after announcing in late May, Tillis raised just $278,000 through the end of June.

With a widening and potentially competitive GOP primary, a big third-quarter number would help solidify Tillis as the party’s front-runner. Hagan has turned in two strong quarterly fundraising reports already, and the crowded GOP primary will allow her to stay focused on building for the future.

4 Rep. Tom Cotton, R-Ark.

The freshman congressman, a favorite of both the national party and the tea party, announced his candidacy in early August and should have no trouble raising money to take on Pryor, arguably the most vulnerable incumbent in the country. But Pryor outraised Cotton in the second quarter 2-to-1 and ended June with nearly four times as much cash on hand.

This race is a top target for outside spending, but Cotton’s first report as an official candidate will offer another sign of how much trouble Pryor is in next year.

5 Sen. Thad Cochran, R-Miss.

The six-term senator is the last remaining incumbent on retirement watch. Unlike many of the seven senators who have already announced they won’t seek re-election in 2014, Cochran would not be leaving behind a vulnerable seat — Mississippi is heavily Republican. After raising less than $200,000 in each of the first two fundraising quarters, Cochran has given no indication yet which direction he’s leaning.

But The New York Times recently reported that Cochran has begun stepping up his fundraising efforts — usually a sign of an intention to run again. After taking office in 1978, his exit would surely unleash plenty of pent-up ambition among Republicans. But strong fundraising might also help Cochran ward off a potential primary challenge from a state senator.