Ms. Fitzgerald said she did not remember reading the email and that if she had read it, she would not have had the power to intervene. Mr. Varadkar defended her, saying he was willing to risk a quick election instead of giving in to opposition demands.
But faced with the prospect of fighting in a deeply unpopular winter election, the members of Varadkar's party, Fine Gael, began to question their continued support for Mrs. Fitzgerald once it became clear Monday that she had in fact, she was informed several times about the intentions of discrediting the complainant.
The episode is a major blow for Mr. Varadkar, who became prime minister in June. Mr. Varadkar, who is a homobadual and the son of an Indian immigrant, was widely hailed as a new youthful face in Irish politics, despite advocating widely conservative economic and social policies.
The agitation comes at a highly sensitive moment. The Dublin government must present its case at the border between the Republic of Ireland, which will remain a member of the European Union, and Northern Ireland, which is part of Great Britain, at a European Union summit in Brussels in the middle of December.  Currently there are no border or customs controls between the two countries, and Dublin is pushing to maintain that agreement. Freedom of movement and trade was a crucial component of the 1998 Good Friday Agreement, which effectively ended 30 years of armed conflict in Northern Ireland.
Northern Ireland faces a political crisis of its own after its rival politicians have not resolved their differences and put an end to the paralysis of a power-sharing administration that has maintained peace in the region for almost two decades.
Dublin fears that the reintroduction of any type of border controls would revive political and sectarian tensions. The restrictions on trade and movement would also be a major blow to Ireland's economic ties with Britain, a major export market.
The December meeting is expected to determine whether Britain has made sufficient progress in negotiations over the country's withdrawal to start parallel talks on a trade agreement with the remaining 27 members of the bloc.
But if Dublin feels that its concerns about maintaining an open border have not been met, Ireland could try to veto the start of trade talks.
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