The controversy over Donald Trump’s attacks on Captain Humayun Khan’s parents continues to roil the presidential race, and Sen. John McCain has now released a statement condemning the GOP nominee’s recent behavior.

"I challenge the nominee to set the example for what our country can and should represent," McCain writes, in sentences that are bolded and underlined. "It is time for Donald Trump to set the example for our country and the future of the Republican Party. While our Party has bestowed upon him the nomination, it is not accompanied by unfettered license to defame those who are the best among us."

Now, there are several cynical ways to interpret this statement. First of all, McCain still appears to support Trump for president. Additionally, he may be seeking to distance himself from the nominee for his own competitive Senate race, and he may partly be motivated by a personal grudge due to Trump questioning his own war heroism last year.

But in my view, this actually is quite a strong statement. McCain’s language ("defame") is far stronger than that of Paul Ryan and Mitch McConnell, who praised the Khan family and said they opposed Trump’s proposed Muslim immigration ban, but didn’t criticize Trump by name.

More importantly, McCain’s statement is deliberately written as a "challenge" to Trump — which means it is asking for a response. And McCain knows from experience that when he speaks his mind about Trump, he’ll likely provoke a response. (Trump’s attack on McCain’s war heroism, after all, was actually a direct response to McCain telling the New Yorker’s Ryan Lizza that Trump’s supporters were "crazies.")

The question is now whether Trump will continue to dig in, and, if so, whether McCain will follow up his strong words with action.