It's easy to write off Donald Trump as a bizarre American phenomenon — a businessman turned reality star who somehow ended up in the political limelight.

That's not quite right: There's actually something global about the rise of Trumpism, and his blend of extreme hostility to immigration paired with centrist or even at times left-wing stances on elements of the welfare state.

In a wide range of countries across the continent, newish parties — often, though not always, with roots in ideological extremism — are gaining support with platforms that emphasize economic nationalism and anti-immigrant politics, often paired with a more centrist view on the welfare state.

Roughly the Trump ideological mix, in other words, except without the bombastic billionaire. And one of the few exceptions to the trend is Italy, where the main center-right political party has long been led by Silvio Berlusconi, a bombastic billionaire with anti-immigrant views.

Consider the current situation in Sweden: An August 20 poll showed Jimmie Åkesson’s Sweden Democrats Party in the lead for the first time in party history. In Sweden's multi-party system, it only takes them 25 percent to be in first place. But that's a lot better than the 12.9 percent they scored in the country's 2014 parliamentary elections, which, in turn, was a lot better than the 5.7 percent they got in 2010 — and that was the first time they ever managed to win any seats in parliament at all.

Their rise has been astoundingly swift, and it tells us a lot about Trump.

After all, as unlikely as Trump's rise in the polls has been, in some ways the rise of the Sweden Democrats is even weirder. The party has its roots in things like the straightforwardly racist Keep Sweden Swedish, its first official party auditor was a Waffen-SS veteran, and in its early days it tried to forge international connections with David Duke's National Association for the Advancement of White People. The party's growth in part reflects ideological moderation and a move toward mainstream politics.

Trumpism, in other words, is much bigger than Donald Trump or the particular pathologies of the US Republican Party. It's a global phenomenon.

Right-wing populist parties aren't extreme, per se

The kind of political movements we're talking about are often shorthanded as "far-right" in the United States and by their European opponents. This is because several of them have institutional roots in old fascist political movements. But their current ideological positioning is generally much more complicated than that, and some of them have no such institutional roots.

For example, when I read the platform of the French National Front, I found a genuinely extreme and super-right-wing view of immigration combined with a critique of the eurozone and the European Central Bank that would be comfortably at home in a Paul Krugman column. FNF also promised to avoid cuts to France's version of Social Security and to enhance benefits for stay-at-home moms.

The Danish People's Party and the True Finns are both friendlier to the Nordic welfare state than are the more traditional center-right parties they are currently allied with in coalitions.

The UK Independence Party manifesto promises to increase NHS funding and to start an early retirement option for Britain's social security system.

The Freedom Party in the Netherlands blew up a center-right cabinet by refusing to endorse an austerity budget.

These policy positions reflect the social basis of political support for unorthodox right-wing parties. Skepticism of immigrants and immigration tends to be more concentrated among older and working-class voters, and older working-class people are inclined to be worried about things like government funding for retirement programs and health-care programs.

The right-populist policy mix is popular

As Lee Drutman detailed for Vox, the policy blend that combines hostility to immigration with support for Social Security and Medicare is actually quite popular.

This is, roughly speaking, the reason movements of this sort are succeeding in a variety of countries despite a lack of seasoned political leadership. The writers and thinkers who define ideological space have generally decreed that nationalist principles should be paired with small government principles, and cosmopolitan principles should be paired with economic egalitarian principles.

But many actual voters see it differently.

In particular, many people are beneficiaries of government programs to support the living standards of the elderly while also being skeptical of the kinds of social change brought about by immigration. Sometimes this can express itself in a kind of "keep the government's hands off my Medicare" ideological confusion. Other times, leaders of mainstream conservative parties can try to square the circle, as when the Republican Party promises to cut Social Security benefits for young people but not for old people.

But it can also manifest itself through the formation of new political parties, or anti-party movements.

Similar trends play out differently because of institutions

In a 2014 paper, law professor David Schleicher observed that institutional differences between the US and Europe can end up obscuring underlying similarities in the development of party politics.

Some countries have proportional electoral systems that are quite friendly to small new political parties that can grab 5 or 10 percent of the vote. In those kinds of countries, there is an extremely strong incentive for newish political movements to found new parties to represent them.

The United States, by contrast, has political parties that are very "open."

You don't need to pay membership fees to vote in a Republican Party primary, and there's no formal institution like a "shadow Cabinet" that officially speaks for the party while it is in opposition. The party is, instead, a loosely defined network of individuals and institutions that is collectively powerful and permeable. Combine that with first-past-the-post voting, and forming a new political party is a generally unappealing option. What you typically want to do is act entrepreneurially within the structure of existing party politics. This is why Black Lives Matter is pressing Hillary Clinton to disavow old Democratic Party positions rather than running its own candidates for office.

If the US had European-style political institutions, Trump would be leading a European-style "far-right" party. Since it doesn't, he's running a GOP primary campaign. But it's gaining support for the exact same reason that populist parties in Europe are.

The populist mix is based on questionable math

The lack of donor support for big government nativism is sometimes cited as a reason that mainstream political parties tend to suppress the populist policy mix. But sometimes combinations of policy ideas are rejected by elites with practical governing experience because they don't quite add up.

Mainstream conservative parties are generally skeptical of spending large sums of money on social welfare for retirees because, being parties of the right, they are committed to trying to keep taxes low.

Populist conservatives tend to brush this away with the implication that if we weren't wasting so much money on welfare for migrants, retirement programs would be easily affordable. This simply isn't true. Productivity growth has slowed in the United States and almost every other rich economy, which puts pressure on the sustainability of the welfare state. At the same time the share of elderly people in the population is growing, which has the same effect. Last but by no means least, health-care services have a marked tendency to rise in cost faster than the economy as a whole — making commitments to comprehensive coverage for the aged expensive.

In most cases, immigration helps on all three scores. More immigration means at least marginally faster productivity growth, immigrants improve the ratio of working-age to retired people, and foreign-born health-care providers help contain the cost of caring for the elderly.