Barely into his 2020 U.S. Senate campaign, John Hickenlooper already has been compared — and not as a compliment — to fellow Democrat Joe Biden, former Democrat Joe Lieberman and Republican Cory Gardner, whose Senate seat the former two-term governor is seeking.

And in large part, that’s coming from members of his own party.

State and county Democratic officers have criticized the Democratic Senatorial Campaign Committee’s endorsement of Hickenlooper, with some accusing the national organization of putting its “thumb on the scale” and “‘interfering/meddling/obstructing’ in our primary process,” according to an email thread obtained by The Denver Post.

Some are comparing the primary to the party’s presidential field, where Biden currently holds the lead over more left-leaning candidates like U.S. Sens. Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, and is the target of their criticism.

Meanwhile, the Republicans gearing up to defend Gardner have been egging on the intraparty squabble, giddily blasting out nearly every Democrat’s attack leveled at Hickenlooper.

Just days after Hickenlooper jumped in the crowded primary, not one of the 11 other Democrats already running in the Senate primary has withdrawn.

While polls commissioned by Hickenlooper supporters have shown the popular politician would be the overwhelming favorite in the Democratic Senate primary, skeptics note that it’s still early in the race – precinct caucuses are six months from Labor Day – and wonder whether the state’s Democratic primary voters will pick the familiar centrist or demand a more aggressively liberal nominee.

Through it all, Hickenlooper – who, as a gubernatorial candidate in 2010, famously took a shower with his clothes in a TV ad to demonstrate his disdain for negative politicking – has declined to engage his critics from the left or other Democrats crying foul over his purportedly late entry into a primary for a nomination that won’t be awarded until next summer.

“This is a talented field of candidates, who will all have the opportunity to make their case and voters will make this decision,” a spokeswoman for the Hickenlooper campaign said Monday after six of the seven women running in the Democratic primary signed a letter asking the DSCC to pull its endorsement.

“To be clear, this race is not a coronation of any candidate,” read the letter, which was organized and initially drafted by persistent Hickenlooper critic Joe Salazar, a former state lawmaker and the executive director of Colorado Rising, a group seeking to restrict oil and gas development in the state.

The letter, which pointed out that Colorado has never elected a woman to the U.S. Senate or as governor, was signed by state Sen. Angela Williams, D-Denver; climate activist Diana Bray; organizer Lorena Garcia; former state House Majority Leader Alice Madden; educator and former congressional candidate Stephany Rose Spaulding; and nonprofit leader Michelle Ferrigno Warren.

Scientist Trish Zornio, who didn’t sign the letter, said she’s been clear that she doesn’t support the DSCC endorsement but didn’t have a chance to review the letter before it was submitted.

The “coronation” line echoed Williams, who scorched Hickenlooper on Aug. 22 when he joined the race a week after ending his lagging campaign in the Democratic presidential primary.

In that race, Hickenlooper took aim at ambitious proposals from fellow candidates, including “Medicare for all” and the Green New Deal, which he labelled “socialist” and said risked handing the election to President Donald Trump.

“John Hickenlooper is the new Joe Lieberman,” proposed Rolling Stone’s Matt Taibi in a Monday article suggesting Hickenlooper’s vulnerabilities with Democrats on climate issues could mirror the problems the former Connecticut senator ran into in a 2006 primary over his support for the Iraq War.

Andrew Romanoff, a former state House speaker and one of the other Democrats running against Gardner, tore into Hickenlooper for “echoing [Gardner’s] talking points” on climate change and health care.

“Cory and John have attacked these progressive priorities as socialist or Stalinist. That’s outrageous,” Romanoff said in a statement.

After the DSCC endorsed Hickenlooper, Romanoff combined the attacks in a tweet: “The @dscc has no qualms at all-they recruited a candidate to fight the #GreenNewDeal & #MedicareForAll, and now they’re doubling down on their investment. We can bend to Washington’s will – or break them.”

The other Democrats in the primary include former state Sen. Mike Johnston, D-Denver, former Obama-era ambassador Dan Baer, and former U.S. Attorney for Colorado John Walsh.

The dust is far from settled, but a Democratic operative and occasional political analyst agreed the national Democrats should let Colorado decide on its own Senate nominee even while cautioning progressives against going too negative, potentially doing the Republicans’ work for them.

“I don’t understand why the folks in Washington, D.C., haven’t gotten the memo that people don’t like it when they meddle in primaries,” Ian Silverii, executive director of ProgressNow Colorado, said in an interview. “Let us fight our own fight out here.”

Added Silverii: “I think primaries are good. They force the party to reckon with the coalitions, they force candidates to define their votes, to really think through their positions and come up with reason those positions were a certain way and are a certain way now, if things are different.”

Silverii said he was concerned about some of the scorched-earth attacks on Hickenlooper.

“The way those can do damage is if we burn down the house on the way to the real [election] cycle,” he said. “This isn’t about coronating anybody, this isn’t about trying to play it safe and easy. It’s a chance for each candidate to define what they’re going to do for Colorado. And once the primary’s over, we’ll do just like we did in 2018 – unite and beat the bad guys.”

Hickenlooper’s opponents haven’t been the only ones swinging hard.

Curtis Hubbard, a political consultant and Hickenlooper supporter – he registered domain names for a Hickenlooper Senate campaign before the candidate had dropped out of the presidential primary – provoked a backlash on social media Tuesday when he pointed out in a tweet that the three other Democratic primary candidates who have run statewide all lost their races and encouraged “any of the other no-hopers” to step aside.

“Time for pretenders to drop vanity projects,” Hubbard wrote, after noting that Hickenlooper has twice won election as governor, while Johnston, Romanoff and Madden all came up short when they were on the statewide ballot in primary or general elections. (Johnston came in third when he sought the Democratic nomination for governor last year, Romanoff lost a 2010 primary against U.S. Sen. Michael Bennet, and Madden lost a 2016 bid for University of Colorado regent at-large.)

A few Twitter users – including Matt Whitlock, a senior advisor to the National Republican Senatorial Committee – proclaimed that Hickenlooper’s presidential campaign was considered a “vanity project” by some, while others slammed Hubbard for a message they deemed “a bit … caustic.”