Time is running out for Republican presidential hopefuls not named Donald Trump.

While this is only the second Republican presidential candidate debate and the start of balloting for the party’s nomination is still almost four months away, the former president has had a durable lead over his rivals for months now.

Tonight’s debate could be the last chance for these candidates to manufacture a dramatic moment that gets their supporters to open their wallets and keep them afloat long enough to have a shot at besting Trump at the ballot box.

Here are some of the key moments so far – and follow our live coverage for the latest updates and analysis.

Are Ron DeSantis’s gloves finally coming off?

Early in the Republican debate, Chris Christie took a swipe at Donald Trump for adding to the national debt while he was president. That was not surprising or new from this longtime Trump critic. What happened next, however, was.

Mr DeSantis quickly chimed in and said that the former president was “missing in action” because he skipped this debate and should have been on the stage to defend his deficit spending as president.

The Florida governor’s quick trigger on an attack indicates he may be pivoting from his past efforts to avoid taking the former president head-on. That strategy hinged on Mr DeSantis being a clear and attractive alternative for 2020 Trump voters who have grown tired of the former president.

But Mr Trump’s base has been sticking with him. So Mr DeSantis may have decided he has to take the former president down if he wants to have any hope of catching him – or even closing the gap – in the polls before voting starts in January.The problem for Mr DeSantis, of course, is that it’s a lot harder to land blows on a candidate who is more than a thousand miles away. So the governor’s “missing in action” swipe could reveal a hint of frustration at his current predicament.

The Republican Party used to be the pro-business, anti-union party. As South Carolina Senator Tim Scott has pointed out, Ronald Reagan – in whose presidential library this debate is taking place – fired federal air traffic controllers when they went on strike in 1981.Republican sensibilities on this matter seem to be changing, however. And like a lot of changes in the Republican Party, it’s because of Donald Trump has shifted the party’s base toward working-class voters.This new sensibility was well illustrated by Vivek Ramaswamy’s response to a question about the striking autoworkers in Michigan, saying he has “a lot of sympathy” for the striking workers who “have gone through a lot of hardship.”There once was a time when every Republican on a debate stage would have condemned a striking union and sided wholeheartedly with businesses on the other side of a labour dispute.

This story will be updated throughout the debate.