WEST LAMPETER, Pa. – Buoyed by an energy veteran political operatives could only compare to the election of President Barack Obama in 2008, Democrats appear to be on the verge of winning back the House of Representatives and potentially winning a slew of competitive governor’s races in Tuesday’s midterm elections.

But the party is at risk of losing ground in the United States Senate, where significant losses could lock it out of power in the upper chamber for the foreseeable future.

At the center of it all are two major issues: President Donald Trump and health care. An NBC News/Wall Street Journal poll released this week found 40 percent of respondents said they wanted their vote in the midterms to send a signal of opposition to the president, while 32 percent said they wanted to use it to send a signal of support. Months of public polling have found health care to be the top issue in the election, with Democrats holding a strong advantage in public opinion.

Those two factors, combined with a surge of grassroots energy that has kept Democratic campaign coffers full and campaign offices brimming with volunteers for door-knocking. National Democrats are as confident as ever in predicting gains in House and gubernatorial elections.

“We’re looking at more Democratic governors, across a broad swath of the country,” said Jay Inslee, the governor of Washington state and the chair of the Democratic Governors Association, who had just come from an event for Georgia gubernatorial candidate Stacey Abrams. “There’s reason to be confident that more than half of the population of America will have a Democratic governor by midnight on election night.”

Inslee’s group has provided key assistance to Abrams and another rising progressive star, Tallahassee Mayor Andrew Gillum, in their bids for higher office. Democrats are optimistic that Gillum, who will spend election night rallying with Diddy at his alma mater, Florida A&M, will triumph over former GOP Rep. Ron DeSantis. In Georgia, however, both parties are now preparing for the likelihood of a costly run-off between Abrams and Republican Secretary of State Brian Kemp.

Prognosticators now view it as likely that Democrats will win the 23 seats they need to reclaim control of the House. Republicans have all but ceded more than a dozen seats, and Democrats need to win fewer than half of the toss-up seats to claim Congress’ lower chamber.

In states like Pennsylvania, where Democratic Gov. Tom Wolf is expected to cruise to re-election by a comfortable margin, the coattails of a popular chief executive could benefit Democratic House candidates in races that would likely not be competitive in an ordinary midterm election year. Some of those contenders in the Keystone State are Ron DiNicola, an attorney running in a district that includes Erie; George Scott, a military veteran and pastor running in a district that includes Harrisburg; and Jess King, a progressive Mennonite and nonprofit leader from Lancaster City.

All of these candidates, if they win, are expected to do so on the backs of white suburban women. In the NBC/Wall Street Journal poll, Democrats have a 55 percent to 37 percent lead over Republicans among female voters. Men favor Republicans by a narrower margin, 50 percent to 43 percent.

There’s reason to be confident that more than half of the population of America will have a Democratic governor by midnight on election night. Gov. Jay Inslee (D-Wash.), Democratic Governors Association chair

Amanda Roth, who has two children, earns a comfortable salary from her work at a small accounting company in Lancaster County. A self-described fiscal conservative, Roth remains a registered Republican and does not regret her vote for former Gov. Chris Christie in 2009 when she was living in New Jersey.

But on Saturday, Roth was spending her afternoon knocking doors for Jess King, the Democrat challenging freshman Rep. Lloyd Smucker (R) in one of the few Pennsylvania districts where Democratic fortunes soured after court-ordered redistricting in 2011.

Like many of the suburban women flocking to Democrats this election cycle, Roth is motivated by her disgust with President Donald Trump, whose xenophobia and boorish conduct she says she cannot abide.

Yet when she described her passion for King as a candidate, she brought up health care, not Trump. Roth has soured on employer-sponsored insurance after years of enduring costly, inadequate coverage. Her current plan has a $6,000 deductible, so she tries to avoid going to the doctor.

“For as long as I’ve been working, I’ve wanted a single-payer system,” she told HuffPost while picking up her canvassing materials at a volunteer’s house-turned-field office. Overhearing Roth, King stepped over to offer her a high five.

Although King’s district, which Trump won by 26 percentage points, is not even a secondary target for national party organs like the Democratic Congressional Campaign Committee, a late October poll showed Smucker with just a 4-point lead.

Regardless of the outcome, King’s competitive bid and the crossover support she has attracted for an unabashedly progressive platform underscores just how ominous the political landscape is for House Republicans on Tuesday.

With top Democrats confidently predicting a House takeover, Republican Party leaders are scrambling to limit the size of a Democratic majority.

That has taken the form of both last-minute efforts to buttress hitherto secure incumbents like Reps. Glenn Grothman (Wis.) and Brian Mast (Fla.) and distance themselves from figures like Iowa Rep. Steve King, whose sympathy for white nationalism is a liability in other parts of the country.

Over the weekend, the major Republican super PAC charged with defending the GOP House majority, Congressional Leadership Fund, launched a six-figure get-out-the-vote campaign to save Alaska Rep. Don Young, the longest-serving member of the House, who is facing a tougher-than-anticipated challenge from independent Alyse Galvin.

If Democrats do face a downside on Tuesday, it will likely be in the all-important United States Senate. Democrats faced one of the toughest political maps in history, defending incumbents in 10 states Trump won. They are likely to lose the North Dakota seat held by Heidi Heitkamp, and seats in Missouri, Indiana and Montana are also at risk.

Democrats have pick-up opportunities in Nevada and Arizona, and early vote data in both states have made them more optimistic. They’re less confident of making gains in Tennessee, where moderate former Gov. Phil Bredesen is facing arch-conservative Rep. Marsha Blackburn, and in Texas, where political phenom Beto O’Rourke is more likely than not to fall to Sen. Ted Cruz. They’re also confident of keeping a seat in Florida held by Sen. Bill Nelson, which Republicans had once promised GOP Gov. Rick Scott would take easily by using his personal wealth to outspend the Democrat.

Still, if Republicans manage to win a majority of the toss-up races, a smaller Senate map in 2020 could make it difficult for Democrats to reclaim control of Congress’ upper chamber until 2022 or 2024. Trump has concentrated his campaigning in recent days in states with competitive Senate races and ended Monday night in Cape Girardeau, Missouri, where he is rallying with the state’s youthful attorney general, Josh Hawley.

However, polls over the weekend looked good for Democratic Sen. Claire McCaskill in Missouri, who is battling Hawley.

“She definitely has the energy, and the field effort is better than anyone I’ve seen in Missouri. Momentum is on her side,” said Abe Rakov, who managed Democrat Jason Kander’s Missouri Senate bid in 2016. “It’s going to come down to the environment of Missouri, and whether her ground game is enough to overcome that.”

Statewide races throughout states where Trump surged ― Pennsylvania, Wisconsin, Michigan, Iowa and Ohio ― look good for Democrats. The four incumbent Democratic senators in those states are safe, and Gretchen Whitmer is all but certain to win Michigan’s gubernatorial contest. Democrats have strong chances to finally defeat Gov. Scott Walker in Wisconsin and to win in both Iowa and Ohio.

“This is a significant confidence builder for the Democratic Party that we can be competitive in the Midwest,” Inslee said.