ALTOONA, Pa.—Two constants have marked 74-year-old Oliver Smith’s life: He’s a lifelong Pennsylvania resident and a lifelong Democrat. One of those is about to change—and he has no plans to leave the Keystone State.

“It seems like the Democratic Party has changed,” Smith said after an event for seniors at Calvary Baptist Church in Altoona, Pa., where he is a member. “They’re going too far, as far as being liberal, letting people in the country that hate us.”

Smith, a retired schoolteacher and state employee, is a solid Donald Trump supporter, even though he voted twice for Barack Obama. But ask him about the state’s U.S. Senate race between Republican Sen. Pat Toomey and Democrat Katie McGinty, and Smith is less sure of himself.

“I haven’t decided on that,” he says with hesitation. “All I have to go by is what I hear on the TV, and probably most of that is lies.”

The 2016 election results may well rest with voters like Smith, who illustrates the growing frustration, shifting political alignment, and lingering uncertainty many people are experiencing. He also highlights the complicated path to victory for endangered GOP senators such as Toomey.

While Pennsylvania could hold the keys to both the White House and control of the U.S. Senate, it’s possible they will fall different ways. Some recent surveys have shown Trump polling ahead of Toomey, who has distanced himself from his party’s controversial presidential nominee and not even pledged to vote for him.

Toomey’s approach makes him simultaneously more attractive to establishment Republicans and suburban independents but less attractive to blue-collar voters who may be poised to flip the state red for the first time since 1988. Last April, Trump’s unique appeal fueled a massive primary turnout that nearly doubled Mitt Romney’s 2012 vote total.

“There’s no question Trump is a phenomenon” in the central and northern parts of Pennsylvania, Republican state Rep. John McGinnis told me. “No one in history brought out as many voters as he did in the primaries. If he does the same in November, he could well win the state.”

Toomey is far from alone in his struggle to strike the right tone with Trump, especially after a 2005 videotape surfaced showing the GOP nominee bragging about sexually assaulting women (Trump later dismissed the comments as “locker room talk” and denied doing what he described in the video). Sen. Kelly Ayotte, R-N.H., has consistently battled Trump-related controversies, yet she’s one of several GOP senators who regularly outpoll Trump—a group that includes Sen. Rob Portman of Ohio and Sen. John McCain of Arizona, two incumbents many had believed vulnerable after they drew quality challengers.

Arizona is usually a reliable red state, but it’s one of several new battlegrounds in the age of Trump. Senate races in Missouri and North Carolina—once assumed to be relatively safe Republican seats—are now in a dead heat.

One thing is virtually certain: The incoming president will have nothing close to the 60-seat supermajority Obama enjoyed following his 2008 election. Republicans hold a 54-46 advantage in the Senate (counting two independents who caucus with Democrats), a lead that is likely to shrink by at least two, since GOP incumbents in Wisconsin and Illinois appear headed for defeat.

Early October polling indicated seven races were still toss-ups (see “Races to watch,” in this issue), including one Democrat-held seat and six GOP-held seats. If the candidates holding slim leads emerge victorious, the Senate would see its first 50-50 split since 2001. The new vice president would cast potential tie-breaking votes.

That could be a short-lived arrangement, if Democratic Sen. Tim Kaine becomes vice president in a Hillary Clinton administration. Virginia Gov. Terry McAuliffe, a Democrat, would appoint a replacement to fill Kaine’s seat until a special election in November 2017, when Senate control could again be up for grabs.

Republicans are already working behind the scenes to land a top-tier recruit to run next year in Virginia. Two GOP possibilities: former Virginia Attorney General Ken Cuccinelli and former presidential candidate Carly Fiorina.

The window for Democratic control is small: A cycle featuring 25 Democrats (including two independents) and only eight Republicans up for reelection looms in 2018. Two years later, Republicans will defend 22 seats, but almost all of them are in red states.

In the event of a 50-50 split, a single senator could hold up judicial and cabinet appointments and take Washington gridlock to a whole new level.

To avoid that scenario, both parties are working overtime to generate excitement in places like Pennsylvania, where high-profile surrogates are stumping for presidential and Senate candidates. The Clinton campaign infrastructure dwarfs the Trump operation, which is more focused on holding large rallies, but Democrats still worry lower enthusiasm for Clinton among Obama supporters may lead to lower turnout.

Outside groups on both sides are pouring money into the Senate race at what could end up a record pace. Americans for Prosperity (AFP), a conservative organization sitting out the presidential election, is one providing support for Toomey. Using its sophisticated voter database, AFP has made 1.2 million calls and knocked on 92,000 doors for Toomey without talking about Trump, the Los Angeles Times reported.

Progressive groups are tying their Senate and presidential candidates together—seemingly unconcerned that Clinton’s unpopularity is nearly equal to Trump’s. That may be a pivotal miscalculation.

It’s easy to drive for hours through central Pennsylvania and see only Trump yard signs. I asked state Rep. McGinnis if he’s seen any Clinton signs: “One less than [Libertarian candidate] Gary Johnson—and I’ve seen one Gary Johnson,” McGinnis said with a wry smile. He said Trump signs are “all over the place. I think Trump might be in the real estate business in central Pennsylvania.”

House call

Sixty days before the 2016 election, House Minority Leader Nancy Pelosi, D-Calif., declared control of the House could be in play—if Hillary Clinton defeats Donald Trump by 6 to 8 points. As the calendar turned to October, Clinton’s polling lead remained under 4 points, leaving Republicans increasingly bullish on their chances. That confidence evaporated after The Washington Post reported on Trump’s lewd comments from 11 years ago, prompting House Speaker Paul Ryan to abandon his party’s nominee.

Democrats were already poised to gain seats two years after Republicans lost only one incumbent and built their largest majority since World War II. A half-dozen seats appear to be easy Democratic pickups, compared with only one likely Republican pickup.

According to the nonpartisan Cook Political Report, 14 out of 17 toss-ups are currently Republican seats. Even if Democrats swept all 17, that would give them a net gain of only 22—resulting in a 224-211 Republican majority.

Many Democratic challengers are trying to tie their GOP opponents to Trump, but few have made efforts to distance themselves from Clinton, who is upside-down by a 2-to-1 margin in some congressional districts. Polling shows many voters believe Clinton will win the presidency and want congressional checks on her. —J.C.D.