"You’re not likely to talk to cocky Democrats who went through 2016. The way the environment moved back [to Republicans] is still a fresh wound,” said J.B. Poersch, president of Senate Majority PAC, the leading Democratic Senate super PAC.

This cycle, party leaders recruited candidates with varied levels of political experience — ranging from governors in Montana and Colorado who dropped out of the presidential race, to several unsuccessful 2018 House candidates with proven fundraising chops. National Democrats helped steer their preferred nominees through primaries in most races, and across the country candidates raised record-shattering sums of money to put Republicans back on their heels.

“We’re not going to take anything for granted,” Sen. Catherine Cortez Masto (D-Nev.), chair of the Democratic Senatorial Campaign Committee, told POLITICO in an interview last week. “We have steadily moved this map to a place where there are more competitive toss-up races than we need to take back the majority. And that expands our options — it gives us more potential paths to flipping the Senate. But we have a lot of work ahead of us.”

The DSCC has booked nearly $50 million for TV ads in four races: Arizona, Iowa, Montana and North Carolina, all states President Donald Trump carried in 2016. Rather than expand elsewhere, the committee recently more than doubled its investment in Iowa, where Democrat Theresa Greenfield is challenging Sen. Joni Ernst, and more than tripled its investment in Montana, where Gov. Steve Bullock is challenging Sen. Steve Daines. Democrats now have more than $17 million booked in both states, and ads attacking Ernst and Daines hit airwaves Wednesday.

Senate Majority PAC has invested in those four races, plus Colorado, Maine and Georgia, where they added $7 million over the next month, their largest investment yet. But they’re also playing defense, including a new seven-figure TV buy in Michigan, one of just two potentially competitive Democratic seats, after Republicans made their first outside investment there in months.

The party’s spending reflects two realities: Thanks to massive fundraising by candidates in places like South Carolina, Kentucky and even Alaska, races in tougher states look potentially competitive without much outside help. But if the environment rebounds for Republicans this fall to put those reach states out of play, Democrats' would still be focused on their simplest path to a bare majority .

“It's a little too early to wave our hands and say we're going to pick up a bunch of extra seats,” Poersch said. “But clearly — as we've been seeing for some time — the majority is in play, and Democrats have a good shot at getting it.”

Republicans are counting on the environment improving this fall, as it did in the closing weeks of the past two cycles, to narrow the field of competitive races as they fight to grind out a majority. Even a minor rebound for Trump nationally would drive races in red states further back in their direction.

“I do think they're in a good position right now," GOP pollster Chris Wilson said of Democrats. "But the map with Democrats is like Charlie Brown trying to kick the football, and the environment is always Lucy pulling it out underneath them."

Still, Republicans have been forced to play defense deeper into red territory than they expected at the outset of this cycle. Republican groups have invested tens of millions in nine GOP-held states, from blue-tinted Colorado and Maine, to deeper-red Montana and Kentucky — and only two Democratic ones, Alabama and Michigan.

"You can safely assume that wherever we have investments are areas where we have an opportunity or concern,” said Steven Law, president of the super PAC Senate Leadership Fund. “Nothing says 'I care' more sincerely than a multimillion-dollar media buy.”

The National Republican Senatorial Committee has raised record sums, and spent heavily starting earlier in the summer than usual. It’s a strategy similar to 2016 when the committee made major investments over the summer to buoy vulnerable incumbents, and super PACs filled in the gaps in the closing days of the election, with most toss-up races going their way.

The NRSC spent nearly $30 million in July — more than in July and August combined four years ago — with $22 million in independent expenditures for TV ads. Republicans say the investments have paid dividends: Their recent internal polling show upticks in the unfavorable ratings of Democratic challengers in a handful of races, including Arizona, Iowa, Montana and Maine.

"Democrats have had their scandals and socialist agenda exposed all summer, and their image ratings have plummeted because voters finally saw what was behind the curtain,” Jesse Hunt, a spokesperson for the NRSC, said in a statement, saying the ads highlight how "totally unfit they are to represent their respective states."

Democrats roundly dispute that — and say their polling shows not only that Republican ads didn’t substantially alter those races, but that Democratic candidates' positive images remain steadily higher than their negatives.

Lauren Passalacqua, a spokesperson for the DSCC, said despite the GOP advertising blitz Democrats have “strengthened their standing with voters in these battlegrounds and put more states in play.”

The issues Democrats are running on mirror the party’s strategy from 2018: Focus relentlessly on health care and other kitchen-table issues, and paint GOP senators as unwilling to stand up to Trump, particularly on the president's pandemic response. They made a similar case against GOP senators and Trump in 2016, said Celinda Lake, a veteran party pollster. But then, it was “more about the individual. In 2020, it's more about the agenda.”

Cortez Masto, who won her first race in 2016, said candidates are defining themselves as independent, while Republicans on the ballot “have been totally unwilling to be a check on the White House.”

Republicans remain confident in their class of senators — the incumbents up this year were last on the ballot in 2014, the year the GOP won the Senate majority — arguing that they have been through the rigors of nationalized, competitive campaigns and will handle the scrutiny better than less-tested challengers.

“While I would love to have the Democrats’ cash-on-hand advantage, I would trade it for the quality of our candidates,” said Law, the president of the GOP super PAC.

Democrats who remember 2014 scoff at that. Adam Jentleson, who was a top aide to then-Democratic Leader Harry Reid, said his party made the same arguments about candidate quality before incumbent senators were swept out across the map when the party lost 8 seats.

“I remember saying all these things we see Republicans saying now. But the reality was the national environment overwhelmed everything, and we didn't stand a chance,” Jentleson said. “That was a significantly less bearish national environment for us than Republicans are facing right now.”

Democrats are laser focused on the 50th seat — the number they need to control the chamber if Joe Biden wins. But they’re also keeping half an eye on a scenario where the rosy summer environment sticks after Labor Day.

"You could plausibly look at a scenario where you say we peaked in the summer and we grind out a couple of seats,” said a Democratic operative who has been involved in multiple Senate races in recent cycles. “You could also look at a scenario where things stay bad and continue to really beat on the president and Republicans.

“We can't look to the future and figure this stuff out,” the Democrat added. “We have to run the best campaigns we can and hope for the best.”