The Republican presidential nomination is up for grabs.

Given his enduring popularity with GOP voters, former President Donald Trump remains the front-runner. While he has yet to formally join the race, Florida Gov. Ron DeSantis has been cast as his principal opponent for the Republican nomination. In past elections, the presence of two high-profile contenders might have been enough to deter other aspirants. But former South Carolina Gov. Nikki Haley's announced candidacy Tuesday and anticipated declarations by other prominent Republicans indicate that many in the party are unwilling to commit to a candidate.

While the presidential election is still 20 months away, the likelihood that multiple credentialed candidates will pursue the nomination also suggests that the Republican Party is open to change, whether in a more moderate direction or toward more conservative policy extremism.

Both Trump and DeSantis appear formidable, at least in public. They dominate the polls nationally and in the early states and have received the bulk of early endorsements from high-profile Republicans. There is no obvious political comparison to Trump in the modern era, but any former president is presumed to be a strong candidate. His polling numbers among Republican voters are still good, and he has far more support from the Republican Party than he did in his first run in 2016.

While Trump might wind up with the nomination, it's significant that other contenders clearly aren't frightened of publicly opposing him. It tells us that many Republicans believe that Trump will be in a worse position when voters in Iowa and New Hampshire make their choices early next year. And their hesitation is understandable for several reasons, not the least of which is that the former president is facing multiple investigations that could lead to criminal charges.

As for DeSantis? He is sitting at around 30% of the Republican vote in early polls, which is remarkably high for a first-time national candidate at this stage in the process. DeSantis is almost certainly doing so well because he has been boosted by conservative talk-show hosts and others in Republican-aligned media, making him the obvious alternative to Trump for some voters. That level of support could be hard to maintain, but most Republicans would rather have the backing of key media personalities than a bunch of random politicians.

But it appears that a lot of Republican politicians and operatives aren't sold on DeSantis, either. Perhaps it's just a matter of his being a first-time national candidate who hasn't proven himself on a national stage. But if his behind-the-scenes support from donors, campaign professionals and Republican media were rock solid, other presidential aspirants would stay on the sidelines, as they did when George W. Bush locked up support from the party network early in 2000.

It takes a lot of time and effort to run for president, and no one with a good reputation wants to be labeled a loser. Nor do they want to go on the attack against someone they believe has a good chance of winding up in the White House.

That isn't what is happening for 2024 Republicans. Haley, a former United Nations ambassador, is only the second conventionally qualified candidate (after Trump) to formally announce. But at least seven others, including former Vice President Mike Pence, are doing everything that candidates do at this stage in the process, such as hiring staff, giving campaign-like speeches and even running ads. Add Trump and DeSantis, and there are 10 candidates total with conventional qualifications. That would be only one shy of the most announced candidates either party has produced - the 11 such efforts for Republicans in 2016 and Democrats in 2020.

When Republicans set their record for the most candidates in 2016, it was in an election cycle unusually lacking in seemingly intimidating contenders. No one had been a nominee for national office, much less having served as president or vice president. Nor were there any returning candidates who seemed particularly strong, although former Senator Rick Santorum and former Arkansas Governor Mike Huckabee had won a few primaries in previous bids. The nomination looked wide open. That's when marginal candidates choose to run.

It's possible that Trump's 2016 nomination has generated a heavy dose of "anything is possible" thinking among Republican politicians. But there sure are a lot of Republicans who think they know something about how open the nomination is. I wouldn't be quick to dismiss that.

Jonathan Bernstein is a former professor of political science at the University of Texas at San Antonio and DePauw University.