Labor Day marks the unofficial home stretch of the campaign season, as campaigns and outside groups ramp up persuasion and mobilization targeting key races. 

With groups beginning to make hard choices about where to spend money, the marquee races down the stretch are looking just as they did to start the cycle—Republican-held seats that Democrat Hillary Clinton won in 2016. 

Here are the 10 House races that have drawn the most television and radio spending between Labor Day and today, according to figures from Advertising Analytics (spoiler: most broke for Clinton in 2016). 

CO-06: $9.2 million

It's no surprise that GOP Rep. Mike Coffman's seat has seen a boat-load of spending in recent weeks—Democrats see the race as one of their best chances to dethrone an incumbent, which is why two-thirds of the recent spending came from the left. Polls show the race will be tough sledding for Coffman, and while his top-spending ally, the Congressional Leadership Fund, has pulled its advertising dollars from the seat, the National Republican Congressional Committee is upping its investment. 

MI-08: $8.2 million

This race is another one featuring a seriously vulnerable Republican incumbent, Rep. Mike Bishop, and a strong Democratic challenger in Elissa Slotkin. And it's also another race where CLF has decided to stop spending while the NRCC ramps up—but limited public polling shows a tight race. 

FL-26: $7.7 million

Republican Rep. Carlos Curbelo's seat was always going to be a marquee race, considering Curbelo is the GOP incumbent representing the district that broke the furthest for Hillary Clinton in 2016. The party committees and the two campaigns have been slugging each other for the past month and aren't expected to slow down. 

VA-10: $7.7 million

The ad spending to defend Republican Rep. Barbara Comstock's seat tells two stories. CLF hasn't spent a dime in the race as polling continues to show Democrat Jennifer Wexton with a lead. But the NRCC is doubling down on the seat—it spent almost $2.6 million since Labor Day, more than any other group, and has another $2.5 million booked through Election Day. 

MN-03: $7.5 million

Republican Rep. Erik Paulsen has long been able to weather the storm in a blue-leaning district, but the heightened spending here shows Democratic enthusiasm that they can finally take him down. Two recent public polls show Democrat Dean Phillips leading. 

WA-08: $7.3 million

The significant spending here is indicative of GOP bullishness for their candidate Dino Rossi and their unwillingness to cede the liberal-leaning district to Democrats after longtime Republican Rep. Dave Reichert announced his impending retirement. But Democrats have matched the GOP spending since Labor Day in the hopes of flipping another seat that Clinton won. 

NJ-03: $7.1 million

The battle for Republican Rep. Tom MacArthur's seat is a good test case for lots of dynamics this cycle. MacArthur has had to own his key role in crafting the GOP's failed healthcare plan and being the only New Jersey Republican to vote for the party's tax plan. But the district leans conservative, so it remains to be seen how those votes might resonate here. 

TX-07: $7 million

Democrats are hopeful that strength with suburban voters can help flip this Dallas-area seat. But Republican Rep. John Culberson has kicked his campaign into gear since early-cycle concerns he was going to be caught sleeping and Republicans outspent Democrats here by $900,000 since Labor Day. 

ME-02: $6.4 million

This is another district where an oft-vulnerable Republican, Rep. Bruce Poliquin, is trying to hold on. A recent New York Times/Siena College poll pegged Poliquin up by 5 points. 

CA-10: $5.9 million

If you're sensing a trend, voters narrowly backed Clinton in this district in 2016. Republican and Democratic spending has been about even here, as Republican Rep. Jeff Denham looks to win another term against Democrat Josh Harder.