CLEVELAND — Hillary Clinton ramped up her pressure on Donald Trump in the election’s most competitive states Friday with an emotional TV ad targeting his criticism of a Muslim-American family. Trump vowed to go all-out in the final three weeks so he’ll have no regrets — even if he loses.

The nominees retrenched behind familiar arguments a day after appearing together at a charity event that veered into cutting personal attacks, an unexpected metaphor for this year’s take-no-prisoners presidential campaign. Clinton’s new ad features Khizr Khan, whom Trump assailed after Khan spoke at the Democratic National Convention.

In the minute-long ad, which Clinton’s campaign said was airing in seven battleground states, Khan retells how his son, Captain Humayun Khan, died in Iraq seeking to protect his US military unit from a suicide bomber.

‘‘Mr. Trump, would my son have a place in your America?’’ the father asks, tearing up as the ad fades to black.

Trump focused some of his criticism on Michelle Obama, who has emerged as one of the most effective voices for Clinton. One of the country’s most popular Democrats, Obama for years has been loath to devote significant time to campaigning, but has done so in recent days with searing indictments of Trump’s treatment of women.

The typically self-assured Trump was unusually candid about the possibility of losing the election, a prospect that’s grown in likelihood as Clinton solidifies her lead in battleground states.

Trump said he is packing his schedule with campaign events so he will know he spared no effort even if ultimately unsuccessful.

‘‘I will be happy with myself,’’ he said.

Associated Press