Democrats believe that Mitt Romney’s troubled presidential campaign is at least in part to blame on his struggle with his own party. The pragmatic former governor of Massachusetts would be hard pressed to persuade right-wing voters that he is conservative as they are.

To an extent, that is true. Romney is less ideologically and perhaps more instinctively conservative than many Republicans. He seems incapable of making the philosophical argument for limited government. But Romney’s problem is only part of a bigger and more radical shift in American politics.

Fareed Zakaria lays out the Democratic argument in his column in The Washington Post this week where he writes, “the problem is not Romney but the new Republican Party” which has moved in an “extreme” direction. Specifically, he cites its resistance to tax increases.

It is obvious that, with a deficit at 8 percent of gross domestic product, any solution to our budgetary problems has to involve both spending cuts and tax increases.

Republicans disagree and have presented several plans, Congressman Paul Ryan and Senator Tom Coburn among others, that achieve higher revenue through tax reform but cut spending more drastically. (Actually, they cut expected spending increases. Under all plans, from Democrats and Republicans, public-sector spending would continue to rise in real terms if not as a percentage of GDP.)

Zakaria points out that even Presidents Ronald Reagan and George H.W. Bush, champions of small government, agreed to raise taxes but he doesn’t mention that they had little choice because Democrats controlled Congress in their times.

In 1982, after enacting historic tax cuts with overwhelming congressional support, President Ronald Reagan agreed with Democrats to raise business and excise taxes in exchange for $280 billion in spending reductions over six years. Taxes went up but so did spending, by $450 billion, $140 billion of which was allocated to defense. Revenue increased by $375 billion during the remainder of Reagan’s tenure.

A couple of years later, Bush struck a similar deal with Democrats. Despite his campaign pledge not to raise taxes, he accepted a “balanced” approach that included spending cuts and tax increases to mend the deficit. Except the spending cuts, again, never materialized and Bush lost reelection in 1992.

Republicans say that they’ve learned their lesson, that Democrats will never honor an agreement to reduce spending, so why should they raise taxes?

This isn’t an extreme position, nor is it a departure from Republican orthodoxy. What has changed is that the party, by and large, has grown more hostile to government than it has been for the last twenty years. As Politico reported last month, “Republican rhetoric is dismissive of any positive role for government that makes the ‘compassionate conservative’ ideas of George W. Bush seem like a very distant echo.”

But Democrats have shifted as well. They are “openly protective of big government in a way it was not during the Clinton years,” writes Politico, evidenced by their wariness of free-trade agreements and their resistance to Medicare reform.

The Republican instinct to reward individuals for risk taking and the Democratic instinct to emphasize collective responsibility will play out in the near term over Medicare. If Mitt Romney and the Republicans win, it’s clear they genuinely would seek to inject substantial private-sector competition into the Medicare program — a fundamental change. President Barack Obama genuinely does view such an experiment as a violation of the social contract.

At stake are issues worth fighting over. On many, from Medicare and tax reform to education, immigration and the future of Social Security, Democrats and Republicans have taken opposite positions.

It’s misleading to berate one party’s vision as “extreme” and say the other’s is pragmatic when it is, in fact, equally ideological and partisan. There is nothing wrong with that. It is why Americans have two political parties to choose from.