Middle-class Americans — defined as those with college, but not a postgraduate, degrees and household incomes between $50,000 and $100,000 per year — are a growing segment of the voting population and increasingly decide the outcome of national elections. Their interests suggest they should vote Republican but the right’s rhetoric is pushing some into the Democrats’ arms.

Both parties have their relatively reliable voting blocs. Democrats have been able to attract enough young and minority voters to make up for a shrinking white working-class electorate. Blue-collar voters with low-income service jobs have increasingly leaned Republican.

Both trends appear to have accelerated in recent years: the 2008 election of Barack Obama saw a high number of young and minority voters turn out while more white working-class voters shifted to the Republican Party in subsequent elections.

If these movements cancel each other out, it are middle-class Americans who represent the swing vote.

They backed Republicans Ronald Reagan and George W. Bush as well as Democrat Bill Clinton. In 2006, 49 percent of them supported Democrats in the midterm elections. Two years later, 50 percent voted for Barack Obama against 48 percent for John McCain. In last year’s congressional elections, support for Republicans had risen to 54 percent.

The number of middle-class voters is growing, The National Journal‘s John B. Judis has pointed out.

In the 1980 presidential election, the white working class made up about 65 percent of the electorate; by 1988, it was 54 percent; by the 2008 election, it was just 39 percent. […] On the other hand, voters with college degrees but not postgraduate degrees went from 26 percent of the electorate in 2004, to 29 percent in 2012, to 31 percent in the last election. And according to census estimates, turnout among middle-class voters is 10 percentage points or more higher than among working-class voters. So middle-class voters are a force to be reckoned with.

Around 70 percent of the middle-class Americans is white but race alone does not explain their voting behavior. At least for Hispanics, support for Democrats has been lower in recent elections among middle-class voters than the Hispanic population at large. (There is no comparable polling for Americans of Asian descent.)

When they have college degrees, jobs, a mortgage, student debts to pay off and need to start saving to get their own children through college, voters are more likely to support law-and-order and low-tax policies, regardless of race — especially when the opposite is leaving them poorer.

Although the economy is growing again and adding jobs, Federal Reserve data show that families in the middle of the income scale still earn less and their net worth is lower than at the start of Obama’s presidency.

Whether it is the lack of job security, unaffordable higher education, a health care system that is similarly more expensive than it needs to be or the absence of real wage growth, the defining question of the next election will likely be how to make life a little easier for those tens of millions of Americans who identify as middle class.

Judis predicts that the Democratic nominee in 2016 — likely to be Hillary Clinton — will struggle to win as many middle-class votes as Obama did. She will “have to shoulder the size-of-government and who-benefits-from-tax-dollars grievances created by Obama’s initial spending programs and by the Affordable Care Act,” he argues.

The Democrats’ best chance of keeping the White House is if Republicans nominate a candidate from the populist or the religious right who will scare off middle-class voters with hardline rhetoric on issues like abortion, gay marriage and immigration.

Middle-class voters tend to be more socially liberal than white working-class voters. And although social issues are not their priority, they will punish Republicans if they go too far.

This website has argued that it is the better-educated, better-off, urban or suburban middle class of whatever race in swing states like Florida, Ohio, Pennsylvania and Virginia that is voting against their interest in lower taxes and less government because they think reactionaries — like Texas firebrand Ted Cruz; “homosexuality is a choice” Ben Carson; and “legitimate rape” Todd Akin — are just repugnant characters. They want nothing to do with a party like that.

If Republicans are smart, writes Judis, they will nominate a candidate “who runs from the center-right, soft-pedals social issues, including immigration, critiques government without calling for abolishing the income tax and Social Security, and displays a good ol’ boy empathy for the less well-to-do.” Someone who can speak to middle-class concerns without alienating the white working class — because Republicans need them both.

The nominating contest for the 2016 election is shaping up to be a test of Republicans’ willingness to follow Judis’ advice.

Candidates like Jeb Bush and Marco Rubio are striking a more conciliatory tone on social issues, have relaxed views about the country’s changing demographics and argue that policies should help Americans get ahead.

Others, like Carson, Cruz, property magnate Donald Trump and Wisconsin governor Scott Walker, are speaking out against gay marriage and immigration and appear to have no idea how to arrest the middle class’ decline.

The Atlantic Sentinel argued last month that by largely steering clear of divisive social issues, Bush and Rubio can build a conservatism that is contemporary and popular. They have a Republican agenda to meet today’s challenges. But if they fail to beat Cruz and the other throwbacks in this year’s presidential primaries, it might very well take another election defeat before the party is ready to accept it.