Democratic Senate Leader Chuck Schumer is sounding increasingly bullish about his party's chances of riding a potential blue wave into November, declaring Democrats have "the wind in our sails" as national and battleground polling points to a favorable political environment in the midterm elections. But beneath that confidence are three variables that could determine whether the Democratic advantage becomes a wave — or breaks before Election Day: a potential polling undercount of Republicans, persistent voter skepticism of the Democratic brand, and the GOP’s financial firepower advantage.

Schumer, speaking to reporters last week as the Senate adjourned until after Election Day, predicted that Democrats are "on the edge of taking back the Senate."

After nearly two years of President Donald Trump back in the White House and Republican control of the Senate and the House, Schumer emphasized, "Americans are frustrated with higher costs and a government they don’t believe is working for them." AI IS SUPERCHARGING THE CAMPAIGN AD WARS, BUT VIRAL DOESN'T MEAN VICTORIOUS The GOP is fighting political history, which has traditionally seen the party in power in Washington lose congressional seats during midterm election years. Add to that a challenging political climate fueled by persistent inflation Americans see at the grocery store, high gas prices tied to what polls show is an unpopular war with Iran, and Trump's negative approval ratings.

The latest polls indicate Democrats holding an advantage over Republicans in the battle for Congress and that they are more enthusiastic to vote in the midterms. But Trump predicts that Republicans will perform much better in the midterms than critics and pollsters expect.

"I think we’re going to have a big surprise, because they don’t know what’s happening," the president told supporters at a rally Saturday night in Ohio, as he referred to Democrats.

Here's a closer look at the three variables. Republicans control the Senate 53-47, which means Democrats need a net gain of four seats to win back the majority. But with one month to go until Election Day, Democrats are treading deeper and deeper into red territory as Republicans stay mostly on defense. The latest Fox News polls indicate margin of error races in Michigan, a must hold for the Democrats, and in Texas, Maine and Iowa, three seats the party is working to flip to win the majority.

An average of the latest surveys also points to very close contests in Alaska, Ohio, and Kansas, where the Democrats are playing offense, and Minnesota, a leading flip opportunity for the GOP. WHO'S UP AND WHO'S DOWN IN THE LATEST FOX NEWS MIDTERM POWER RANKINGS But what if the polls are off?

"Polls considerably underestimated Donald Trump and other Republicans on the ticket with him in 2016, 2020, and, to a slightly lesser extent, in 2024," polling guru, political analyst and statistician Nate Silver noted this past weekend. But Silver added that polls in the previous two Trump-era midterms, 2018 and 2022, were essentially unbiased.

Fast-forward to this cycle, and polls in some high-profile Democratic primaries were off the mark.

Among the miscues this summer, overestimating Abdul El-Sayed's narrow victory in Michigan's Senate showdown, and underestimating victories by Lt. Gov Peggy Flanagan in Minnesota's Senate primary, state Rep. Angie Nixon's win in Florida's Senate contest, and Milwaukee County Executive David Crowley's upset victory to capture the Wisconsin gubernatorial nomination.

Coverage of the miscues grabbed widespread media attention and sparked fresh criticism of public opinion polling.

DEMOCRACY ’26: STAY UP TO DATE WITH THE FOX NEWS ELECTION HUB If the surveys are overestimating Democratic turnout and underestimating Republican enthusiasm, even a modest polling miss could reshape several of the close Senate contests. "I don't think any Democrat is over optimistic after...2024.

We all understand that anything can happen in the closing days, and we're preparing for that," longtime New Hampshire Democratic Party Chair Ray Buckley told Fox News Digital.

Trump's approval ratings remain well underwater, as do favorable ratings for the GOP.

But surveys indicate the Democrats' brand is nothing to brag about. The Democrats' favorable rating hovered in negative territory in the most recent Fox News national poll, at 44%-55%. And it was even lower in the latest Wall Street Journal national survey, at 38% favorable and 58% unfavorable.

"I think just because Americans are outraged because of how Republicans have failed them and made their life more expensive doesn't automatically mean that they're going to embrace and trust Democrats," former Biden administration Transportation Secretary Pete Buttigieg told Fox News Digital on Saturday. Buttigieg, a 2020 Democratic presidential candidate who is considering another White House run in 2028, said it's crucial Democrats "make sure that our candidates get out there, make it very clear who they are, what they're about, and what we would do differently."

Making life even tougher for the Democrats: the victories by left-wing and socialist-aligned candidates over more moderate contenders in the party's primaries, which gave the GOP more messaging ammunition to portray all Democrats on the ballot this year as radicals.

SIGN UP TO GET THE POLITICS NEWSLETTER That's the case in Michigan, Minnesota and Florida, where El-Sayed, Flanagan and Nixon all defeated establishment-backed rivals.

Meanwhile, in Texas, a trail of controversial past comments by Talarico is handing the GOP more firepower.

But Democrats in all four of these Senate showdowns are returning fire by anchoring the Republicans on the ballot to Trump.

In the latest Fox News poll in Texas, 53% of those questioned said they were extremely or very concerned that Talarico is too liberal.

But a near equal amount, 51%, said they were extremely or very concerned that Paxton is too close to Trump. Republicans are winning the ad wars, thanks to a major money advantage.

Boosted by massive cash infusions from the Trump-aligned MAGA Inc. and other leading Republican groups and donors, the GOP is outspending the Democrats in all of the crucial Senate showdowns. That includes a roughly $70 million advantage in Ohio and nearly $30 million in Maine and Texas, three top targets for the Democrats, according to figures from AdImpact, a top ad-tracking firm. The GOP's outspending the Democrats by approximately $25 million in Michigan, which Republicans are aiming to flip.

Republicans are also outspending Democrats in swing state New Hampshire, in the battle to succeed retiring Democratic Sen. Jeanne Shaheen. "The amount of money being spent is enormous," Buckley told Fox News Digital, as he pointed to all the Republican-aligned ads flooding the small state.

But Buckley said Democrats have organizing and enthusiasm advantages.

"We might not be as competitive as we'd like on television, but we're certainly competitive knocking on the doors. We've got the energy out there. The voters are excited.

You saw that with the turnout in the primaries throughout the country," he said.