Iowa state Sen. Joni ErnstJoni Kay ErnstOvernight Finance: McConnell, Schumer spar over debt limit | WH says tax reform depends on Dems | Mnuchin doubts Trump’s corporate tax goal possible | Dem wants criminal probe of Equifax stock sales | Mystery surrounds Cordray’s plans GOP senator calls for caps on ex-presidents' benefits Senate approves Trump's debt deal with Democrats MORE (R) had a huge fundraising quarter, bringing in more than $6 million from July through September.

Those numbers are upward revision of the $4.5 million Ernst's campaign initially announced last week, and more than double the $2.8 million for Rep. Bruce BraleyBruce BraleyOPINION | Tax reform, not Trump-McConnell feuds, will make 2018 a win for GOP Ten years later, House Dems reunite and look forward Trump: Ernst wanted 'more seasoning' before entertaining VP offer MORE's (D-Iowa) team in a race that could determine Senate control next year.

"I'm incredibly thankful for the substantial outpouring of support," Ernst said in a statement. "People are joining our campaign because they know the status quo in Washington isn't working. As we enter the final stretch, we have the momentum we need to take the Iowa way to Washington."

Braley had previously built a big fundraising advantage and had $1.6 million more in the bank heading into the quarter.

Ernst has $3.2 million cash on hand. Braley hasn't announced his cash on hand numbers but had $2.7 million in the bank as of the end of June. It looks like Ernst, with the help of a number of big-name Republicans, could have more money for the campaign's homestretch, though outside groups from both parties are spending heavily on the race.

—This post was updated at 9:35 a.m.