CORONADO, Calif. — As party leaders prepared for a Republican National Committee meeting in California, Sen. Amy Klobuchar was in Iowa, the latest Democrat to fuel speculation about a 2020 presidential bid.

The early Democratic jockeying to take on President Trump has not gone unnoticed on the other side of the aisle — and Republicans concede there are quite a few potentially formidable contenders.

In interviews with two dozen operatives, strategists and officials around the country, Republicans placed the most credible Democratic candidates into categories: the rising congressional stars (Kamala Harris) and the pure political outsiders (Mark Cuban), the fiery progressives (Elizabeth Warren) and the pragmatic moderates (John Hickenlooper).

And of course, there’s Joe Biden.

Republicans stressed it is far too soon too pick a front-runner, much less worry about how that person might pick apart Trump. Plenty of Republicans interviewed couldn’t offer a name — just a type of candidate — noting that Democrats are at war with themselves over the direction of their party and will have an intense primary process.

And at the RNC, there was already discussion of Trump’s re-election. At a closed-door lunch at an oceanside resort here, Trump’s daughter-in-law Lara Trump enthusiastically noted her involvement with the 2020 effort in a short speech that was well-received, according to attendees.

With those caveats, here is how Republicans are handicapping their rivals’ possible 2020 contenders.

THE SENATE STARS

In the leadup to 2016, a host of Republicans used the Senate as a platform to build national brands that eventually launched presidential campaigns. Republicans recognize that the same could be true for Democrats this time around. Cory Booker of New Jersey, Harris of California, Kirsten Gillibrand of New York and Klobuchar of Minnesota all are drawing attention, even as many of them insist they aren’t interested in running.

In interviews with RNC members in California and with Republican operatives across the country, Booker — a social media-savvy former mayor of Newark — and Harris, a former California attorney general, generated the most buzz.

“He’s young, charismatic, and he’s a smart guy,” Glenn McCall, the Republican national committeeman from South Carolina, said of Booker — though he added that he expects the American people to “reward” Trump with re-election.

A Republican state chair agreed, saying Booker “might be able to reassemble the Obama coalition.”

“Cory Booker is perceived as a moderate,” added Vincent Harris, a Republican operative. “He is well-liked, has the ‘want to get a beer with you’ appeal and as someone who sat next to him accidentally at a concert this year, he is charming and easy to talk to.”

Harris, the freshman senator from California, is already making a name for herself on Capitol Hill as a progressive and a sharp Trump critic.

“I’d say the most intriguing potential candidates for the 2020 Democratic nomination are the ones who aren’t has-beens or retreads,” said Republican strategist Ryan Williams, who served as a longtime aide to 2012 nominee Mitt Romney. “People like Kamala Harris and I guess Cory Booker, who are somewhat new faces in the party.”

On the other side of Capitol Hill, there is Democratic Rep. Seth Moulton of Massachusetts.

“Generational change, decorated combat veteran, smart, good on TV, good command presence,” said Steve Schmidt, who guided Republican Arizona Sen. John McCain’s 2008 presidential campaign.

OUTSIDER WILD CARDS

Trump shattered long-standing expectations for the kind of governing credentials a presidential hopeful should have. If the outsider mood that put him in the White House prevails, that could open the door for a number of prominent public figures who also lack traditional political experience, Republicans say, even though replicating Trump’s path would be a long shot.

“If I were a Democrat, I’d try to go for someone like a Mark Cuban or Mark Zuckerberg that has outsider appeal and could compete with Trump,” said Saul Anuzis, a former Michigan Republican Party chairman. “If you could find somebody who’s viewed as a true outsider, that would shake things up.”

Zuckerberg, the Facebook founder, has generated speculation about his political plans for the last several months, after announcing intentions to visit and meet with people from all 50 states. Recent stops have included Ohio and Michigan — two Rust Belt swing states that helped hand Trump the presidency.

A number of Republicans also pointed to Cuban, the billionaire businessman, television personality and owner of the Dallas Mavericks who is often a vocal Trump opponent.

“I know a lot of Republicans who would be interested in helping him,” said Amanda Carpenter, a former communications director for Sen. Ted Cruz, R-Texas. “He’s conservative on economic issues without all the ideological baggage. Meaning he talks about business, taxes and regulations from a real-world perspective, not a theoretical one. Refreshing!”

Weekly Standard editor-at-large Bill Kristol suggested someone like Sally Yates, the former acting attorney general who was fired by the Trump administration but has been back in the spotlight recently with testimony concerning former National Security Adviser Michael Flynn.

“The best Democratic candidate might be someone with experience but relatively apolitical, apparently centrist and tough yet personable,” Kristol said.

POPULIST PROGRESSIVES

Republicans acknowledge that the liberal Democratic base is energized right now, and prominent progressives such as Sens. Warren, D-Mass, and Bernie Sanders, a Vermont independent, have name recognition and are enormously popular with an activist class that would be happy to see either of them run.

But Republicans also argue that those two lawmakers are so polarizing that they would push even Trump-skeptical moderates back to his corner in a general-election scenario. Someone else from that wing of the party, however, could be competitive.

“Amy Klobuchar,” said Rick Tyler, a conservative strategist and commentator. “An underestimated, talented Midwestern woman who appeals to the Elizabeth Warren-Bernie Sanders progressive base but (is) much more likable.”

BIDEN TRAVELING

On a recent trip to New Hampshire, Biden insisted, “Guys, I’m not running.” But some Republicans think that at this juncture, Biden is among the strongest potential candidates the Democrats could field. In part, that’s because plenty of Republicans don’t think the Democrats have a strong, primed bench, but it’s also in part because Biden is well-respected.

“He is universally well-liked by Democrats,” said Miami-based Republican strategist Ana Navarro. “There is some buyer’s remorse that he didn’t do it in 2016. He’s no spring chicken, but hell, neither is Trump, and Joe keeps himself in good shape. All those other Democratic names popping up feel like a litter of new-born puppies next to Joe.”

Agreed Alex Conant, who served as Florida Republican Sen. Marco Rubio’s communications director on his presidential campaign: “The only name that concerns me at all is Joe Biden. He is the only potential candidate that can unite Obama’s liberal coalition with the working-class swing voters that voted for Trump in 2016.”

ACCOMPLISHED MODERATES

A centrist, pro-business, experienced lawmaker could make for an impressive opponent should he or she survive a Democratic primary, Republicans say, especially if there’s an appetite for a strong contrast with the bombastic Trump. Republicans awarded bonus points to governors, who would have some distance from Washington.

“The candidate who I think makes a ton of sense for the Dems is still from Trump’s generation but is a likable Western (governor), and that is Gov. Hickenlooper” of Colorado, said Rob Stutzman, a California-based GOP strategist.

Carpenter added that Sen. Mark Warner — a former Democratic governor of Virginia — could also fit the mold, noting, “He’s got executive experience, has won in a competitive state and has a very important position on the Senate Intelligence Committee that will give him the ability to speak intelligently about cybersecurity issues threatening American institutions.”

Several Republicans said that even if a more centrist candidate wouldn’t light up the left the way a Warren or Sanders-esque contender would, the base would likely still turn out to try to topple Trump. Someone with crossover appeal, then, would be stronger.

“The left will coalesce behind whoever is the nominee in order to defeat Trump,” predicted one Republican strategist working on 2018 midterm races. “The moderate governor type, the former chief executive type, in my view, is dangerous, because they’ll be able to sway independents.”

Several Republicans also nodded to New Yorkers such as Gov. Andrew Cuomo and Gillibrand, who are hardly conservative Democrats but still have some appeal to the center.

“Cuomo is a powerful governor from one of the most influential states and can maximize media coverage in the leadup to a run,” said Jason Roe, a Republican strategist in attendance at the RNC, who also called Gillibrand “very savvy and telegenic.” “And being from New York, both will be able to raise truckloads of money.”

Of course, some Republicans note, the eventual Democratic nominee will be much more competitive if Trump and Republican-controlled Washington don’t fulfill core promises from the 2016 campaign.

“What scares me is if Republicans don’t fulfill their campaign promises, not just on health care issues but on a lot of issues that we campaigned on,” said Kelly Arnold, the chairman of the Kansas Republicans. “That’s the part that scares me most, not a candidate.”