This election season could go down in history as one of nastiest we’ve ever seen. Not only do the Democratic and Republican presidential candidates have historic unfavorability ratings, but the electorate also is more divided than it has been at any point in the last quarter century.

With this deep partisan divide, politicians have less incentive to pivot toward a shrinking center and be civil. Election reformers, though, think they have a solution to the hostility infecting politics: a system by which voters rank candidates in order of preference, rather than voting for one.

If successful this November in Maine, ranked-choice voting will be used in races for the Legislature, Blaine House and Congress.

But a fix for the nastiness and vitriol in politics won’t be as easy as ranking one… two… three…

We’re more divided than we have been in generations.

The referendum on ranked-choice voting — Question 5 on the November ballot — comes up for a vote at a time of particularly intense partisan division among the electorate, both in Maine and nationally.

Surf through your Facebook feed, cable news shows or newspaper comment sections for a few minutes and it becomes clear Americans are deeply divided over politics. And that division is at a historic high. For the first time since 1994, the majority of Republicans and Democrats see the opposing party “very unfavorably,” according to a Pew Research Center study on polarization, released in June.

When Pew first surveyed Americans on their views of political opponents in 1994, only 21 percent of Republicans and 17 percent of Democrats saw the opposing party in a very unfavorable light. Over time that ideological rift has only widened. Among Republicans polled this year, 58 percent hold very unfavorable views of Democrats, while 55 percent of those on the other side of the partisan division see Republicans in a very unfavorable light.

“It’s clear that we’ve been the most polarized electorate that we’ve seen in generations,” said Daniel Shea, director of the Goldfarb Center for Public Affairs and Civic Engagement at Colby College in Waterville.

Behind this growing mutual contempt is a series of demographic and economic shifts that have caused a great deal of insecurity among swaths of the electorate. The Great Recession and the lengthy recovery left many people feeling economically insecure, especially unskilled workers without a college education, and the rise of the LGBT rights movement and an increasing population of nonwhite Americans shook the cultural status quo, contributing to the growth in polarization, Shea said.

Against this backdrop, the perceived stakes in each election are much higher.

“One of the more disturbing components of this polarization is a growing hostility to the other side,” Shea said. “A growing number of Americans think the members of the other party are a threat to the nation.”

(Pew backs Shea up on this point. Its polarization study found that almost half of Republicans and Democrats viewed the other party as a threat to the well-being of the nation. That makes compromise in Augusta or Washington a hard sell back home.)

That rising partisanship has been matched with growth in the ranks of independent voters, who outnumber both Democrats and Republicans. Maine is no exception, where about 37 percent of registered voters are unenrolled. But when pressed, nearly nine in 10 independents identify closely with one party or the other, according to a 2015 Pew study. Like rank-and-file Democrats and Republicans, the direction political independents lean often is based on the view that the other party’s policies are a clear and present danger to the country.

How to make elections civil again

Proponents of ranked-choice voting have pitched the method as a solution to the growing hostility infecting politics. The idea is that voters can divide their loyalties among multiple candidates, something that could motivate candidates to use less hostile campaign tactics to secure second and third place votes to remain viable in the event of an instant runoff.

Ranked-choice voting isn’t widely used in the United States. Only 11 cities — including Portland — use it to elect representatives to local offices, such as mayor, city council and school board, while the Academy of Motion Picture Arts and Sciences uses it to select winners for the Academy Awards. Nowhere in the U.S. is it used for statewide or federal contests.

The limited political science research on ranked-choice voting’s moderating influence in these cities suggests it has the potential to increase civility in elections. For example, a 2013 survey of candidates in local elections concluded that under ranked-choice voting they ran less negative campaigns than those in cities with plurality elections.

Under ranked-choice voting, 28 percent of candidates said their opponent portrayed them negatively, compared with 40 percent of candidates in plurality contests. Likewise, just 21 percent of candidates in ranked-choice voting elections admitted to attacking an opponent, while 37 percent of their counterparts in plurality contests did the same.

“It changes the way candidates campaign when they have to campaign for second and third place votes,” said Caroline Tolbert, a political scientist at the University of Iowa in Iowa City and a co-author of the survey. “They can’t alienate citizens who are going to vote for somebody else for their first choice because they need their second place or third place vote.”

That change in campaign tactics appears to have made a difference, with voters reporting that local elections were more civil after adopting ranked-choice voting, according to a 2014 Rutgers-Eagleton survey of likely voters both in cities that used ranked-choice voting and those with plurality contests.

In ranked-choice voting cities, 28 percent of respondents said that candidates spent a great deal of time criticizing one another, compared with 36 percent of respondents in cities with plurality elections. When asked how the 2014 election compared to prior contests, 18 percent of respondents in ranked-choice cities said it was less negative, while 13 percent said the same in plurality cities.

To what extent this is the result of a switch from a plurality system to ranked-choice voting, however, isn’t clear. No surveys have yet to capture the transition from one to the other. While respondents report that local elections were more civil, it’s not clear whether other factors could account for the difference.

Nasty politicking can get winning results.

But national and state contests don’t fit the profile of elections in which ranked-choice voting would have an impact on nasty politics. Campaigns for local offices are more civil than those further up the ballot because candidates are “so well-known at the local level” that it discourages negative campaigning, Shea of Colby College said.

Polarization right now is deeply entrenched at the congressional level, and the dysfunction and partisan divisions are starting to trickle down to state legislatures.

Maine voters, though, have shown strong support for independent candidates, at least for governor — Eliot Cutler in 2014 and 2010, Barbara Merrill in 2006, and Angus King in 1998 and 1994. That could be make Maine elections civil again as their opponents would need to vie for potential second or third place votes, Tolbert said.

Still, the candidate who moderates her position may find the space between the ideological poles a lonely place. Recent elections have shown more voters stick with one party or the other in the poll booth, while fewer swing between the parties. Swing voters — whose ideological allegiance shifts from election to election — now comprise about 5 percent of the electorate, down from a high of 15 percent in the 1970s, according to a 2015 study by political scientist Corwan Smidt of Michigan State University in East Lansing.

“Party elites can ignore the moderating specter of floating voters because polarization has changed many of them into loyal supporters,” Smidt writes.

That reality isn’t going anywhere.

Rather than rebuking them, voters throw support behind candidates who are anything but clean and tidy. The rise of politicians such as Donald Trump and Gov. Paul LePage is evidence that nasty politicking is “a winning formula,” Shea said.

Ahead of his 2014 re-election bid, LePage caught flak for a series of offensive statements that led some observers to doubt his ability to secure a second term in the Blaine House. If voters intended to hold him accountable for his rhetoric, they failed to do so: LePage captured 48 percent of the vote, a 10 percentage point increase over his victory for a first term.

The vitriol and nastiness we hear from politicians is a reflection of the attitudes of a deeply polarized electorate. That’s the product of deep, long-term shifts in American life, and reversing it will take time.

“It’s not going to be quick [a return to civility],” Shea said. “There’s a whole bunch of forces [at work] that likely won’t change.”