Republican and Democratic voters, making drastically different assumptions about the politics of the 2016 presidential race, are pulling their parties even further apart — setting the stage for a historic ideological battle in 2016.

Opening his MSNBC show shortly before the first Democratic debate, liberal Chris Hayes was ebullient.

Socialist insurgent Sen. Bernie Sanders has been rising in the polls and drawing huge crowds, and front-runner Hillary Clinton, rather than putting him on the defensive, has been eager to embrace a broad liberal policy agenda.

This has been a welcome development to Hayes, who noted that as a progressive who came of political age during the Bill Clinton era, he remembered "a time when the conventional wisdom in the Democratic Party was you needed to convince everyone that you weren't George McGovern, and you need to convince particularly white swing voters you weren't just going to hand out welfare to the other people that don't look like you. You're going to be tough on crime, you're going to fight wars, you're going to fly back to Arkansas to watch a man executed."

But this time around, things were different. "I still can't believe what I'm seeing," he said, gleefully.

Hayes was not alone among liberals celebrating the leftward shift within the Democratic Party. "The Elizabeth Warren wing of American politics has clearly shifted the center of gravity in the Democratic Party," the Progressive Change Campaign Committee boasted in a statement following the debate. "This was the first presidential debate in history where debt-free college, expanding Social Security benefits, breaking up Too Big To Fail banks, and criminal prosecution of Wall Street bankers were big issues."

What's happening in the Democratic Party is that President Obama's two election victories have given its voters confidence the demographics of the nation are working in their favor. Mitt Romney won the white vote by 20 points — the same margin as Ronald Reagan did in his landslide victory over Jimmy Carter — and yet this wasn't enough to overcome Obama's advantage with non-whites.

Democrats figure that the coalition of unmarried women, minority groups and young voters aren't going to back a Republican nominee who wants to defund Planned Parenthood, support voter ID laws, crack down on illegal immigration, oppose efforts to combat climate change, protest gay marriage, and so on. Given their growing confidence that the changing face of America is with them, Democratic voters feel more comfortable letting their liberal flag fly in a way that Bill Clinton would have never dreamed of. His ever-calculating spouse has made the calculation, in the words of the New York Times' Jonathan Martin, that "there's no gen[eral] election downside in aligning w[ith] the left."

Republicans, on the other hand, are making a completely different calculation. Looking ahead to the 2016 campaign, they see Hillary Clinton's numbers steadily tanking under an ethical cloud, as a growing number of Americans say they don't trust her. Polls have shown Republicans ahead of Clinton even in Pennsylvania, a blue state that has eluded GOP nominees for decades. They're confident that her weaknesses as a candidate have made the presidency ripe for the picking. Given this sense of optimism, they see no reason to settle.

Instead, as of this writing, half of Republican primary voters polled nationally are supporting candidates who have never held elective office. At the same time, candidates who fit the profile of a traditional Republican nominee (such as Jeb Bush and Ohio Gov. John Kasich) are at about 10 percent — combined. It's true that it isn't totally fair to pin this all on ideology rather than a more abstract rebellion against anything smacking of the Washington Establishment. Donald Trump, an avowed supporter of tax hikes and single-payer healthcare, won't win any conservative purity tests, despite his hardline rhetoric on immigration. But still, when the dust settles, it's difficult to see the Republican electorate deciding that to beat Clinton, they need an "electable moderate" in the mold of Bob Dole, John McCain or Mitt Romney.

Two electorates, both smelling victory, see no reason to cede policy ground. Ideological warfare is sure to follow.