In 2006 and 2008, American voters gave Democrats big victories because they were mad at Republicans. In 2010, they gave Republicans a big victory because they were mad at Democrats.

Every poll on the subject shows that the voters don’t want the two parties to fight all the time, but to work together to get their problems solved.

But the parties don’t get it. Democrats, dominated by liberals, think that their victories are a mandate for expensive, bureaucratic government programs and higher taxes to pay for them.

Voters don’t want that, so they vote in Republicans — who, dominated as they are by conservatives, think they were put in to hack away at government, cut taxes, and, not incidentally, evict illegal immigrants, outlaw abortion and keep discrimination going against gays.

Voters have proved before they don’t want right-wing policies any more than they want left-liberal policies, but what they get is a clanging of the political pendulum from right to left, when most voters are centrist to somewhat conservative.

Both parties habitually marginalize political moderates, who make up close to a majority of the overall electorate.

As scholars William Galston and Elaine Kamarck point out in a new paper, the polarization of U.S. politics is not just “dysfunctional” but downright “pathological,” resulting in “politics as warfare in which contested issues are never resolved but endlessly relitigated.”

“A nation that cannot adopt and then hew to a steady course is by definition incapable of solving problems that require sustained and widely supported purpose,” they write.

Galston and Kamarck are both Democrats, veterans of the Clinton White House, and they make the point that winning the moderate vote is more important to their party than it is to the GOP.

The basic arithmetic is this: In election after presidential election, exit polls show that, on average, 47 percent of voters self-identify as moderate, 33 percent conservative and 20 percent liberal.

Democrats need 60 percent of the moderate vote to win presidential elections. Republicans can get by with less than 40 percent, but both parties woo moderates — then ignore them when the election’s over.

In their paper, written for the centrist group Third Way, Galston and Kamarck recommend steps for empowering moderates so that politicians are more likely to seek problem-solving consensus instead of pandering to their base vote.

One is open or “blanket” primaries in which candidates from both parties run against each other and the top two face off in a runoff election.

At present, primary elections tend to be low-turnout affairs in which the most militant partisans carry the day. In Washington state, turnout in the 2010 “blanket” primary was nearly three and a half times the average in other states.

California passed a referendum last year opting for the system, which will represent a major test, because more than one-eighth of all House Members hail from that state.

Galston, of the Brookings Institution, said he’d also favor some states trying the Australian system of mandatory voting — no-shows pay a fine — which also expands turnout.

Kamarck, a Harvard professor, said it would also help if all states held their primaries on the same date. Scattered all over the calendar, they tend to be ignored by most voters.

The two scholars also recommended that Congressional and state legislative lines be drawn by nonpartisan commissions, a system pioneered in Iowa and now working in eight states.

At present, districts usually are gerrymandered to protect incumbents or maintain a heavy partisan majority, discouraging candidates from appealing across party lines.

And the third idea is for Congressional leaders, both Senate and House, to be elected by supermajorities, not simply by the majority party. The scholars acknowledged the idea had no chance of being adopted now but was worth proposing anyway.

For many party activists, “moderate” means “mushy,” but Galston and Kamarck show with poll data that moderate voters have distinct views: skepticism toward government, pro-business and low taxes; liberal on social issues such as abortion and gay rights; and hawkish on Afghanistan, if not Iraq.

Asked whether “God has granted America a special role in human history,” one poll showed that 54 percent of moderates agreed, compared with just 34 percent of liberals.

Moderates are certainly somewhat to blame for their own marginalization. They tend not to show up to vote in primary elections.

With rare exceptions (like me), the term “militant moderate” is an oxymoron. But it’s clear that the parties have built up institutional barriers for moderate influence that ought to be reformed.

Moderate doesn’t just mean middle of the road. It also means measured, rational, logical, deliberate, steady, consensual, results-oriented, tolerant, problem-solving.

I think this is what the public wants. It’s what presidential candidates always say they will be — “kinder, gentler” and “uniter not divider” Republicans, “new” and “not Red or Blue America” Democrats.

But the current system causes them to fail to deliver. Problems don’t get solved — and, persistently, majorities of Americans think that the country is headed in the wrong direction. It shouldn’t be that way.