JERUSALEM — Hillary Clinton suggested in a television interview in Israel, broadcast on Thursday, that the Islamic State is “rooting for Donald Trump’s victory” and that terrorists are praying, “Please, Allah, make Trump president of America.”

Speaking with Israel’s Channel 2, Mrs. Clinton said that by singling out Muslims during his campaign, Mr. Trump had played into the hands of extremists and helped their recruitment efforts, in effect “giving aid and comfort to their evil ambitions.”

The stark language was aimed at undercutting Mr. Trump’s support among those who see him as stronger on national security and deflecting critics who have complained that Mrs. Clinton and President Obama do not take the threat of radical Islam seriously enough. The suggestion that an enemy of the United States might favor an opponent’s election was once a red line in American politics, but in a year of bombastic charges and countercharges, there seem to be few lines left.

Mrs. Clinton’s assertion came in response to a question from the anchor Yonit Levi about why she does not use the term “war on radical Islam,” a frequent critique from the political right in both America and Israel. Mrs. Clinton responded that drawing Islam into the equation “actually serves the purpose of the radical jihadists.”