Senate Democrats are posting record fundraising hauls for the midterm elections — but Republicans, boosted by a deluge of secret money, figure to more than keep pace. So if Democrats do end up beating the odds and holding onto control of the chamber, it might be less because of how much money they spent, and more because of how they spent it.

Simply put: While both sides are flooding the airwaves with ads, Democrats are also investing serious money in a ground game of unprecedented strength. And that could make the difference.

Three weeks from Election Day, the Senate rests on a knife-edge. Most analysts give Republicans somewhere between a 50% and 60% chance of picking up the six aggregate seats they need to win control.

Democrats are pursuing a two-pronged strategy: Spend enough on ads to stay competitive, while also investing in major field resources to get supporters to the polls.

Close video A look inside the campaign fundraising process When it comes to raising campaign money, President Obama is no spring chicken - he raised $782 million in 2012, and has attended 55 fundraisers in 2014 alone. Former Gov. Howard Dean, D-Vt., joins to discuss the process of candidates raising money during When it comes to raising campaign money, President Obama is no spring chicken - he raised $782 million in 2012, and has attended 55 fundraisers in 2014 alone. Former Gov. Howard Dean, D-Vt., joins to discuss the process of candidates raising money during share tweet email Embed

The Democratic Senatorial Campaign Committee (DSCC) is spending $60 million on the Bannock Street Project, a turbo-charged, data-driven ground operation that aims to ensure the 2014 electorate looks more like 2012—which saw massive turnout from minorities and young people—than the Republican wave election of 2010. Named for the Denver street where the 2010 campaign of DSCC chair Michael Bennet was located, Bannock Street has said it’s hiring 4,000 paid staff to get out the vote. Republicans have nothing comparable.

“We are investing far more in turnout than the Republicans,” Justin Barasky, a spokesman for the DSCC, told msnbc. “Bannock Street is the largest most sophisticated turnout operation in the history of Senate races.” Barasky’s boss, DSCC executive director Guy Cecil, said in a statement Monday that Bannock Street “is already paying dividends for campaigns across the country as we head towards GOTV.”

In each of four of the tightest Senate races—Alaska, Colorado, Iowa, and North Carolina—Democrats and their allies spent at least three times as much as the other side on voter contact operations, according to numbers compiled recently by the New York Times. In Iowa, Democrats spent over 10 times as much, and in Alaska, around nine times as much.

Of course, it makes sense that Democrats would focus more than Republicans on the ground game. Driving the dynamics of the 2014 contest is the reality that in recent years, Democratic voters—especially minorities and young voters—haven’t turned out for midterms at anywhere near the rate they have for presidential elections. Simply put, an aggressive get-out-the-vote operation is likely to be far more valuable to Dems than Republicans, whose voters tend to show up more consistently. And getting people out for these midterms—at a time when many Democrats are discouraged by the tough slog that Obama’s presidency has turned into—figures to be a much taller order than the 2012 election.

Still, that doesn’t mean the 2012 cycle holds no lessons for this year. That time around, Republicans and their allies enjoyed a clear edge on the air, but Democrats and their allies spent enough to largely turn the air war into a wash, amid evidence that voters got so deluged with TV ads that by election day they’d tuned them out.

Then, Democrats dominated Republicans on the ground. Over a year in advance, the Obama campaign began placing field staff in communities around the country, including many that had rarely been targeted by national political campaigns. The effort relied on grassroots organizing techniques developed by Harvard experts and pioneered by the first Obama campaign, as well as sophisticated data software. In one mark of the Dems’ advantage, the Obama campaign had 122 local offices in the election’s most important state, Ohio, compared to Mitt Romney’s 40. The field mismatch made the difference on election day.

Still, if Democrats are to repeat that strategy, they’ll need to avoid getting blown out in the money and spending race—both to fund Bannock Street, and to stay competitive on the air.

The DSCC announced Monday that it had raised $16 million last month—a record for September. But its GOP counterpart, the National Republican Senatorial Committee, took in just half a million less.

For a while over the summer and early fall, Democrats and their allies enjoyed a clear edge in fundraising and ad spending. Between early July and mid-September, pro-Democratic Super PACs raised four times as much as pro-Republican ones, and outspent them by $60 million to $38 million, according to data compiled by the Wall Street Journal. And in the first two weeks of September, 34,000 pro-Democratic ads aired in Senate races, compared to just 29,000 pro-Republican spots, according to the Wesleyan Media Project, which tracks political advertising.

The pro-Democratic edge was fueled by spending from NextGen Climate Action, the SuperPAC founded by environmentalist Tom Steyer, and by Senate Majority PAC, a group with close ties to Majority Leader Harry Reid.

Republicans sounded the alarm to their donors in response. “Today’s ad deadline is vital. Our candidates are getting massively outspent by Democrat-funded attacks,” one typical recent NRSC fundraising missive read.

There are signs that things are shifting. From Sept. 11 through Sept. 25, Democrats still had about a 3,000-ad edge in the 10 states that Wesleyan monitored. But take away Michigan and Virginia—two states that Republicans don’t need and where they’ve all but given up—and the margin all but vanishes. And in four of the most competitive states—Iowa, Kentucky, Colorado, and Alaska—there were more pro-Republican ads than pro-Democratic ones.

By Election Day, the GOP will likely have an advantage, thanks to two massive conservative groups that don’t disclose their donors. The Koch Brothers’ network reportedly aims to spend a whopping $300 million on this election, and its most active group, Americans for Prosperity has said it will run ads specifically advocating for the defeat of Democrats in the closing days of the race. Karl Rove’s Crossroads GPS has said it will spend at least $23 million in the final two months in six states.

That plan didn’t work for Rove and co. in 2012. The question is whether Democrats’ can make history repeat itself.