The Houston gathering of the Indian diaspora in the U.S. on Sunday addressed by Prime Minister Narendra Modi and U.S. President Donald Trump was a resounding success in meeting its stated and implied objectives. Mr. Modi has drafted Indian diaspora communities in several countries for advancing his strategic objectives. The diaspora in the U.S. is of pre-eminent significance given its increasing political heft and the centrality of the U.S. in India’s strategic architecture. Mr. Trump’s appearance at the rally and his effusive support for India were a reflection of the community’s influence in U.S. politics. He named fighting “radical Islamic terrorism” as a key common interest of the two countries, spurring a standing ovation by the audience, including Mr. Modi. Mr. Trump also emphasised border security, a controversial topic in both democracies. Mr. Modi presented the ending of autonomy for Jammu and Kashmir to the cheering crowd as a significant achievement of this government. The rally galvanised the diaspora in support for Mr. Modi’s politics in India, and enticed Mr. Trump.

The rally’s unintended outcomes could be more complex. The massive movement of people across national borders has created diasporas that, in turn, have created new political forces. This is a particularly sensitive component of global politics. Its enthusiasm for India notwithstanding, aspirations of the diaspora and the priorities of India don’t necessarily converge. Drawing its members too deep into India’s domestic politics, and India’s involvement in their politics, are both fraught with risks. Mr. Modi nearly endorsed Mr. Trump’s re-election bid, and the jamboree was unprecedented for the divisions it created among the diaspora. Civil rights groups and groups of Kashmiris, Dalits and Muslims, who have been critical of Mr. Trump, also called out the Modi government for its policies. Democrats by and large took a dim view of the event, and the audience and Mr. Modi greeted Majority Leader in the House of Representatives Steny Hoyer’s reminder that India drew on its strength of Nehruvian secularism with stony silence. Mr. Trump’s implied endorsement of Mr. Modi’s Kashmir policy was music to the ears of those in the audience, but the underlying principle of his America First nationalism that it has no role to play globally other than protecting its own interests could lead to outcomes not to India’s liking. The absence of four of the five Indian-American members of the U.S. Congress — all Democrats — at the gathering was also noteworthy. The transposition of India-Pakistan rivalry into a contest between the two diasporas is also unpleasant. Despite what Houston achieved for the two leaders, a line may have been crossed in the mixing of partisan national politics with international diplomacy.