In the recent Irish elections, Sinn Féin won 37 seats and took 24.5% of the total vote. Despite this it has been (so far) unable to form a government.

The prospect of it doing so has produced expressions of horror from its rivals in Fine Gael and Fianna Fáil. The outgoing taoiseach, Leo Varadkar, described Sinn Féin plans to hold post-election rallies as part of a “campaign of intimidation”, while in an unprecedented intervention, the Garda commissioner Drew Harris (a former senior officer in the Police Service of Northern Ireland) stated that he agreed with a 2015 security assessment that claimed that the IRA army council still “oversees” the party. Mainstream commentators have echoed these points, stressing that Sinn Féin is unfit for government in Dublin.

This hysteria has several roots. Some evidently dislike the idea of a “northern” party holding power “down here”. Others, usually sotto voce, echo the view of the political correspondent John Drennan who once suggested that Sinn Féin supporters existed on a diet of “chips, Dutch Gold and batter burgers” – a nod to the party’s supporters being mainly working class.

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The negative coverage of Sinn Féin’s breakthrough also reflects annoyance at the disruption of the two-party system, which has served as a comfort blanket for commentators who like to portray Irish politics as “non-ideological”. The result was seismic: the two major parties, which once commanded over 80% of the electorate, and defined themselves in opposition to one another, are now faced with the prospect of either coalescing or sharing power with Sinn Féin.

Despite crude efforts to paint it as part of the rise of the populist right, Sinn Féin’s success is a leftwing phenomenon. The party campaigned on the need for massive public investment to deal with a dire housing crisis and a crumbling health system. Sinn Féin has eschewed anti-immigrant rhetoric; one of its TDs (MPs), Martin Kenny, suffered an arson attack after condemning racist activity. (The Irish far-right characterises Sinn Féin as “globalist”). The party supported both marriage equality and the repeal of laws outlawing abortion in recent referendums. Under proportional representation, Sinn Féin transfers also helped to elect members of smaller socialist parties.

Critics have conjured up the prospect of Ireland becoming another Venezuela if Sinn Féin entered government. But these predictions sound hollow coming from politicians who presided over an actual economic collapse. Sinn Féin was simply best placed to benefit from voters still angry at the austerity period of 2008-2016 and disgusted that there could be almost 10,000 people homeless in a booming economy.

Some suggest the party’s history renders it unsuitable for power. Though the Provisional IRA decommissioned its arsenal and disbanded in the mid-2000s, Sinn Féin honours the legacy of that organisation’s armed struggle. Its opponents argue that “shadowy” northern figures continue to direct party policy. There is no doubt that republican veterans retain huge influence within Sinn Féin. But references to the IRA’s campaign had little impact on the new voters attracted to the party. For them the recession is far more relevant than a conflict that ended 25 years ago.

Ironically the partitionist nature of Irish politics also benefits Sinn Féin. Most voters in the Republic pay little attention to day-to-day northern politics. But what people are aware of is that since 2017 Fine Gael and Fianna Fáil have been demanding that Sinn Féin return to government with the Democratic Unionist party in Belfast. It seems strange then to assert that it is unfit for power in the Republic. Indeed if the IRA army council is really running Sinn Féin, then how does DUP leader Arlene Foster (a woman whose father was actually shot by the IRA), share power with them in Northern Ireland?

For many voters, particularly the young, the exclusion of Sinn Féin is more about the establishment protecting itself than morality. It is true that many of these voters cannot recall the Troubles; neither indeed can some of Sinn Féin’s newly elected TDs. The party’s president, Mary Lou McDonald, herself did not join the organisation until after the IRA’s final ceasefire. But rather than not caring about the violence inflicted by the IRA, as some charge, many note that Sinn Féin’s critics seem solely concerned with republican activities, with no equivalent focus on violence carried out by British or loyalist forces. Since both Fianna Fáil and Fine Gael have roots in the revolution of 1919-21 and declare pride in the “old” IRA, their critiques of Sinn Féin’s past seem hypocritical.

Sinn Féin’s recounting of the conflict is certainly partial. But it is also clearly a party that has been rewarded for involvement in a peace process; most voters were not retrospectively endorsing the IRA’s war or demanding a united Ireland. The rise in British nationalist rhetoric since Brexit also had an impact, reminding voters that Britain had once denied self-determination to Ireland. Early in the election a government proposal to commemorate policemen who fought against the IRA during the revolutionary period also backfired spectacularly.

Sinn Féin’s breakthrough has aroused hopes in thousands of voters that it represents something fundamentally different to the old order; the frenzied efforts to keep it from power have reinforced this view. In 2009 Eoin Ó Broin, one of the most impressive among the party’s leadership, predicted that there might come a time when it would have to either prioritise national unity, perhaps by entering coalition with an establishment party, or make a serious effort to reshape politics to bring about an “independent democratic socialist Ireland”. Sinn Féin no longer says “socialist” in its literature and the more far-seeing of Ireland’s business community have been less hysterical about the election’s outcome than some commentators. Indeed Sinn Féin’s record in government in Belfast often reveals them to be ruthlessly pragmatic.

However it plays out, the old party system in the Republic has been broken for good – another casualty of the great recession. But many of Sinn Féin’s new voters are likely to have no compunction in seeking other political homes if they feel their hopes for change are dashed.

• Brian Hanley is a historian. His latest book is The Impact of the Troubles on the Republic of Ireland