American politics have clearly grown more polarized in recent years. Republicans have become firmly a party of conservatism, not moderation, while Democrats in the Donald Trump era have moved further to the left.

“The problem has been that the folks on the extremes, they’re the most vocal and they’re where the money tends to show up,” says Bruce Bond, cofounder of the Common Ground Committee, which seeks to bring together people and politicians with opposing viewpoints.

So where does that leave moderate voters?

More and more Americans are expressing their unhappiness with the two parties by registering as independents. In a Gallup poll this month, 42 percent of respondents identified as independents -- a dozen points more than Democrats and 16 points higher than Republicans.

“Moderates and the traditional conservatives are politically homeless right now,” says Jack Pitney, a government professor at Claremont McKenna College and a former Republican official who left the party because of Trump. Former First Lady Barbara Bush said that by today’s terms, she would not classify herself as a Republican, according to a forthcoming biography. With Trump’s rise, she said, she saw a party she could not continue to support.

There appears to be ample room left for candidates to appeal to centrist voters. But it’s not clear what centrists want. It’s generally been the case that voters who think of themselves as moderate actually hold quite liberal views on some issues and more conservative views on others. They aren’t looking for politicians who find some sweet spot in the middle of important questions.

“They’re all disaffected for very different reasons,” says Kevin Kruse, a historian at Princeton University. “The hard part about crafting a new party would be to cobble together a coalition out of all these disparate issues.”

Few voters actually swing their votes from one party to the other. Political science research has repeatedly shown that voters who identify as independents may not consider themselves partisan, but they almost invariably do vote in party-line fashion. According to the Pew Research Center, only 6 percent of voters are true independents who don’t lean toward one party or the other. Gallup found that 88 percent of Americans identify with or lean toward one of the two major parties.

“I don’t think there are a lot of moderate voters who are going to flip back and forth,” says Julian Zelizer, Kruse’s Princeton colleague and his coauthor of Fault Lines: A History of the United States Since 1974. “It’s a small sliver of the vote.”

Still, there are a number of voters who are dissatisfied with American politics and the divergent directions the parties are heading. Is either party interested in winning them over?

Campaign Like a Centrist, Govern Like a Partisan

One key factor in President Trump’s election was his ability to win over disaffected Democrats who had supported Barack Obama but were unhappy with the party’s 2016 presidential nominee, Hillary Clinton.

Trump won 206 counties that had supported Obama in 2008 and 2012, which were heavily concentrated in the Midwestern states that propelled him to an Electoral College victory.

“I think Donald Trump actually represented a triumph of centrism,” says GOP consultant Brad Todd. “A lot of analysts never thought you could run on a platform that was socially conservative and fiscally moderate.”

Trump pledged allegiance to conservatives on issues like abortion, gun rights and federal judges, and he has taken a hard line on immigration. But he broke with Republican orthodoxy on issues like trade and foreign intervention, while promising to protect entitlement programs and casting himself as a stronger defender of LGBT rights than Clinton.

“On some levels, he was the least ideologically conservative candidate in 2016 on the Republican side,” says Geoffrey Kabaservice, director of political studies at the Niskanen Center, a think tank that promotes “bold moderation.”

It’s easy to forget that Trump campaigned as something of a centrist because he has governed as a staunch conservative. In contrast with his campaign stances, he has supported deep cuts to Medicaid funding and ordered a ban on transgender people serving in the military, while promoting tax cuts and abortion restrictions.

On Trump’s watch, the remaining moderate Republicans in Congress have nearly all retired or been defeated. “Moderates, at this point, are a severe minority of a minority” in the House, says Kabaservice.

Having won by seizing part of the center, Trump has governed by appealing almost strictly to his base. Will Democrats claim the political space he’s left vacant?

Democrats Move Further Left

The Democratic Party seems to be engaged in an effort to see how far an American party can move to the left. Prominent presidential candidates and other Democratic politicians are variously talking about preserving and expanding abortion rights, talking up a single-payer health-care plan known as Medicare for All, promising to abolish U.S. Immigration and Customs Enforcement (ICE), and seeking to impose severe energy restrictions as part of a Green New Deal.

Such proposals may excite the party’s progressive wing, but they threaten to put off moderate voters who would otherwise be willing to vote against Trump.

“When I said I'm Never Trump, I mean ‘Never,’ and will vote for anyone who isn't Trump,” Tom Nichols, a U.S. Naval War College professor and prominent conservative critic of the president, tweeted last month. “But liberals are already exhausting me and it's only 2019.”

Democrats scored most of their gains at the congressional and legislative levels last fall in affluent suburbs. Sizable numbers of Republican voters -- particularly women -- who had held their nose and voted for Trump over Clinton in 2016 expressed their dissatisfaction with the president by breaking with his party in the midterms. According to the Brookings Institution, 83 percent of Americans live in counties where the Democratic share of the vote increased from 2016 to 2018.

There is now a liberal consensus within the Democratic Party on social issues such as LGBT rights, immigration, marijuana legalization and same-sex marriage, says Ryan Pougiales, senior political analyst with Third Way, a centrist Democratic think tank. But when it comes to the economy and the federal budget, he says, there’s a broader range of opinions.

He notes that during last year’s campaign, Democratic candidates in targeted House races often ran ads on health care, but they raised issues such as affordability, preexisting conditions and Medicare.

“Just two ads, total, talked about single-payer health care,” Pougiales says. “Both those Democrats ended up losing.”

Still, the party’s large and wide-open presidential contest thus far has been a contest to see who can move farthest to the left. That may change, but for now progressives appear to be convinced of the correctness and popularity of their positions, spurning any candidate who veers toward the center or hints at cooperating with the other party.

Progressives nowadays like to deride moderates as wanting only “some” global warming or offering health care to most but not all Americans. The traditional way of finding the center -- working out compromises with political opponents -- has become politically radioactive.

“The problem is that we continue to be in a situation where legislators are concerned that if they’re viewed as working with the other side, they’re going to lose in their primaries,” says Bond, the Common Ground Committee CEO.

Voting on Identity, Not Issues

Progressives are convinced that no matter who the Democratic nominee ends up being or what positions she or he may take, Trump will deride that candidate as a socialist.

That is likely correct. But it’s possible to be progressive on many issues while signaling to voters a willingness to seek the center when appropriate. The new Democratic governors of Kansas, Maine, Michigan and Wisconsin all ran last year on fairly liberal platforms, including support of Medicaid expansion, but broke with left orthodoxy on an issue or two after having defeated more ardently progressive candidates in their primaries.

“The Democrat who can win is progressive but can show a pragmatic side,” says Craig Burnett, a political scientist at Hofstra University. "'I’m not going to try to raise your taxes but will do things to make the country better.'"

Republicans, for their part, believe that Democrats have moved so far to the left on issues such as abortion, guns and the environment that Trump can again command the center in the 2020 election, particularly if the economy keeps humming.

“With Democrats embracing neo-socialist policies to eliminate private health insurance and fossil fuels, America’s political center is up for grabs,” Marc Thiessen, a former Bush administration official, wrote in the Washington Post after Trump’s State of the Union address last month. “[Trump] reached across the aisle, appealed to persuadable voters in the center and asked them to consider his reasonable proposals.”

That assumes that Trump will spend the campaign curbing his usual instincts to appeal to his base and demonize his enemies -- something he’s shown little discipline for during his presidency.

Princeton historian Zelizer notes that even if some voters might hunger for a party that better matches their positions on certain issues, they won’t necessarily vote in large blocs based on such policy stances. A more perfect party fit on policy can’t match the “intensity of red and blue,” he says, hinting at the extent to which identity has become a defining factor in our politics.

Support for the parties is now split not just on ideological lines but by all manner of demographic factors, such as race, gender, geography and church attendance.

“If you’re in a rural or small-town area and you’re white, at this point you’re a Republican,” says Kabaservice, “and if you’re in a city and you went to college, you’re a Democrat.”

American politics has largely become a contest of “us vs. them.” Firing people up has become less a business of defining who “we” are and more about making certain that a majority of voters find “them” completely unacceptable. During next year’s general election, candidates may seek to find persuadable voters, but they’ll spend more time making sure their most likely voters are terrified at the prospect of four years of “them.”

With Trump on the ballot, partisan polarization of a type that’s been familiar now through four presidencies will continue.

“In a traditional election, it’s about the middle,” Democratic strategist Morgan Jackson told McClatchy. “But with Donald Trump, I don’t think the middle exists.”

This story has been updated. It appears in the Politics newsletter. Subscribe for free.