Initial information suggests that the attacker, Omar Mateen, was motivated at least in part by Islamic radicalism, in which case the ensuing debate will center on terrorism, which is already the focus of Trump and other Republicans. Clinton and other Democrats are framing a gun-control debate with the potential extra element of anti-gay hatred, which Mateen’s family members believe motivated him. In addition, he reportedly worked in security and was fully licensed to own guns.

The test for Trump will be avoiding gaffes that would further enrage Muslims after his proposal to ban them temporarily from entering the country. Shortly after noon on Sunday, he tweeted, “Appreciate the congrats for being right on radical Islamic terrorism,” though Matteen’s motivation was far from clear at the time of his tweet. As the presumed Republican nominee, he’ll now be expected to propose a comprehensive response to terrorism. What will it be?

If Mateen was motivated in part by anti-gay prejudice, Trump’s public statements may be revealing on an issue he has largely sidestepped so far. LGBT voters favor Clinton overwhelmingly, and Trump’s core supporters are culturally conservative. But Trump has also, surprisingly, attracted a small band of gay supporters. “Donald Trump is the most pro-gay Republican nominee ever,” Chris Barron, the former national political director of the gay Republican group Log Cabin Republicans, said last week. That assessment is based largely on Trump’s pre-campaign behavior – contributing to AIDS charities, attending Elton John’s wedding, and seeming to support same-sex marriage—though as a candidate he has opposed it. What will he say now?

The test and opportunity for Clinton and for all political leaders is to move these debates forward. Terrorism, gun control, anti-gay bias – these are long-established issues. Republicans and Democrats have dug their trenches, and in trench warfare there’s little movement. The Orlando incident, the worst mass shooting in U.S. history, offers a chance for any leader to say something new and unexpected. That’s risky, of course. We’ll see if anyone is willing to take the risk.

One other angle. I’ve been suggesting for weeks that this year’s Libertarian Party ticket could be a surprise game-changer. Though the party has never won even 1% of the vote in a presidential election, it was attracting 10% support in polling a month ago, then 11% after it nominated former New Mexico Governor Gary Johnson and former Massachusetts Governor William Weld as its ticket, then 12% last week. While Johnson is far from a pure libertarian and Weld isn’t really a libertarian at all, party doctrine has long advocated total abolition of gun control. Johnson and Weld will have to answer very tough questions this week.

This essay appeared in Power Sheet, Fortune’s daily newsletter on leaders and leadership. Sign up here.