ALLENTOWN, Pa. (CBSNewYork/AP) — Mary Heintzelman shakes her head in disgust over the presidential election.

“I don’t think we have a candidate that’s really suitable to be president in either party,” says Heintzelman, an administrative assistant from Whitehall, Pennsylvania. Her son suggests she write in a candidate when she votes in November, but the 68-year-old says despondently, “I don’t even know who to write in.”

Heintzelman is hardly alone in her angst over the prospect of a November matchup between presumptive Republican nominee Donald Trump and likely Democratic pick Hillary Clinton. While 65 percent of Americans say they’re interested in the White House race, just 23 percent say they’re excited as the presidential contest shifts from the primaries to the general election, according to a poll by the Associated Press-NORC Center for Public Affairs Research.

The malaise crosses party lines. Majorities of Republicans and Democrats say the election has left them angry, helpless and frustrated. Only 13 percent of Americans say they’re proud of what has transpired in a campaign where surprising candidates have thrived and Trump in particular has defied political norms.

Election experts say the gap between Americans’ high interest and low excitement makes the race to succeed President Barack Obama highly unpredictable.

Turnout can be low when unpopular candidates are on the ballot, but the unusual nature of a race between a billionaire businessman who has never before sought elected office and a former first lady who would be the country’s first female president could offset voters’ sour mood.

“We’re in uncharted territory here with these two candidates,” said Michael McDonald, a political science professor at the University of Florida who studies voter turnout. He said that while Americans may not be excited about their options, “the negativity gives people something to talk about.”

“If people perceive the election is interesting, they may still show up to vote even if it’s against a candidate,” McDonald added.

Former Gov. Ed Rendell, D-Pa., predicted voter enthusiasm could increase as the general election heats up, particularly when the nominees meet in debates.

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“I do believe in some ways there’s a reset in the general election,” Rendell said. “First of all, you have some voters that paid no attention and only vote in general elections. Secondly, even the ones who paid attention, now all of a sudden there’s two candidates and six months.”

For now, though, some people say they’re resigned to an election in which they’ll be voting against a candidate instead of for one. That view was pervasive in interviews with more than 30 voters interviewed by the AP in Pennsylvania. Democrats have carried the state in every presidential election since 1992, but Trump’s campaign hopes strong support from working-class white voters could swing the state back to the GOP.

“Your vote isn’t who you’re for, it’s who you don’t want in,” Joann Spangenberg, a 48-year-old loan underwriter, said as she stood outside her office in downtown Allentown on a sunny afternoon. “It shouldn’t be that way.”

Spangenberg said the election is generating more interest among her family and friends than in past years, including spurring her daughter to register to vote right after her 18th birthday. But the frequent Republican voter says that while she likely will go for Trump in November, her support is lukewarm at best.

“He’s what we have left,” she said before ducking back into her office.

Pittsburgh voter Kim Bowles feels the same way about Clinton. Bowles has been intrigued by Bernie Sanders, but doesn’t think the Vermont senator can win, leaving her feeling stuck with Clinton as the only option for stopping Trump.

“If you don’t vote, you’re helping someone else, and I’m not a fan of Donald Trump,” said Bowles, 51, as she waited at a bus stop. “So, I’ve got to vote for Hillary. But it’s not easy.”

Trump formally clinched the GOP nomination last week, cementing his extraordinary rise to the top of the Republican Party. Clinton is still trying to shake Sanders, but it’s nearly impossible for Sanders to catch the former secretary of state in the Democratic delegate count.

For Ron Zemlansky, a 64-year-old accountant from Catasauqua, an election between Trump and Clinton leaves voters with two bad options.

“Trump, I don’t think he’s qualified,” he said. “Hillary, there’s too much baggage.”

Despite voting for Obama twice, Zemlansky said his questions about Clinton may push him to Trump.

“Right now, I hate to say it, I’d probably pick Trump,” he said.

The AP-NORC poll of 1,060 adults was conducted May 12-15 using a sample drawn from NORC’s probability-based AmeriSpeak panel, which is designed to be representative of the U.S. population. The margin of sampling error for all respondents is plus or minus 4.1 percentage points.

Respondents were first selected randomly using address-based sampling methods, and later interviewed online or by telephone.

(TM and © Copyright 2016 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2016 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)