(CNN) The 2020 Democratic primary, which already boasts more than 20 candidates , may seem tame compared to a House race in the Bronx.

A couple of months after veteran Rep. José Serrano announced he would retire in 2020, some Democrats in New York and Washington have grown worried that Councilman Rubén Díaz Sr., a 76-year-old, cowboy hat-wearing Pentecostal minister known for his constituent services and controversial statements on social issues, could be elected to Congress in a deep blue district next to one led by Rep. Alexandria Ocasio-Cortez.

While the presidential contenders quibble over policy, this congressional race has already turned personal.

Councilman Ritchie Torres — the first out gay person to hold elected office in the borough and a likely competitor in the race — told CNN, "Rubén Díaz Sr. is the most vicious homophobe in New York State politics."

Díaz, a self-proclaimed "conservative Democrat" is out of step with the national party's views on abortion and same-sex marriage. He was the only Democrat in the state Senate to vote against a bill legalizing same-sex marriage in 2011. And he has been sharply criticized in recent months for saying the City Council is "controlled by the homosexual community"; he was subsequently stripped of his chairmanship of the For-Hire Vehicle committee and urged to resign by the City Council Speaker Corey Johnson.

Díaz did not respond to multiple requests from CNN for comment on this story. He has said publicly that he is in favor of traditional family values and is attacked for espousing them.

"What I said is not homophobic, it's the truth," Díaz told the New York Daily News in February, adding he was the "victim" amid the demands for him to apologize.

But Díaz, who previously served in the New York State Senate for 15 years, is viewed as a strong contender in the campaign with a proven base of support, especially among senior citizens, ministers through his New York Hispanic Clergy Organization and taxi cab drivers.

"No one should underestimate Rubén Díaz Sr.," said US Rep. Nydia Velázquez, who has not endorsed anyone in the emerging race. "The voters know him."

A crowded race emerges

Díaz is set to face Torres and Assemblyman Michael Blake, a vice chairman of the Democratic National Committee who will officially announce his campaign at a rally Sunday, in the primary.

Torres told CNN it is "extremely probable" that he will run for Serrano's seat. He said he would focus on issues like increasing federal investment in public housing, building on his work as the chairman of the relevant committee in the City Council.

In a separate interview, Blake said his record on criminal justice reform issues — including boosting efforts to raise the age of criminal responsibility, banning commercial bail and helping charitable bail organizations assist poor people — can't be beat.

Yet, they both turned their sharpest comments for Díaz Sr. In calling out his controversial statements regarding the gay community, Torres said Díaz Sr. should be running in the Republican primary instead. And Blake called Díaz's rhetoric "absolutely unacceptable," "divisive," "hateful" and "not at all becoming of someone that should be running for Congress or quite frankly an elected office."

A week ago, local media reported that Díaz said at a City Council sexual harassment training session, "I'm not gonna rat my people out!" Legislators including Torres quickly began writing bills to tighten the rules for reporting such incidents. Blake told CNN his comments were "appalling." Díaz responded that the reports had "distorted" what he said, arguing he has "immediately addressed any sexual harassment or bullying if I have even suspected that a woman has felt uncomfortable when someone is violating the rules."

Paul Lipson, a former chief of staff for Serrano, said that aspects of the current congressman's legacy — from restoring the Bronx river to his work on immigrants' rights — will last. "But I do think that the values that he brought to the seat may not endure," he added.

Díaz Sr. boasts multiple advantages in a congressional race, from sharing the same name as his son, Rubén Díaz Jr., the Bronx borough president, to having a defined constituency in a multi-candidate race. And more may come besides Torres and Blake: Marlene Cintron, the president of the Bronx Overall Economic Development Corporation, told CNN she was considering running and will make her decision in June or July.

"If it's more than two candidates running in the same race that he's in, I'm afraid that he is going to be the next member of Congress from that district," said Gerson Borrero, a NY1 political commentator, told CNN. "He does have a base, which is a problem with this guy."

The South Bronx district is poorer and less white than the one next door represented by Ocasio-Cortez. But it's even more Democratic. Serrano, who has served the district for almost 30 years and is the longest-serving Puerto-Rican member of Congress, won reelection in 2018 with 96% of the vote. The demographics of the district — about two-thirds Latino and one-third black—could favor Latino candidates like Díaz Sr. or Torres.

"Our primary voters in the district skew older and slightly, every so slightly more socially conservative than you might expect in such a thoroughly Democratic district," Lipson said. He said that every candidate's challenge will be to motivate people to come out to vote next June, when segments of the electorate, particularly young people, don't.

New York delegation 'monitoring the situation'

All of these factors are on the minds of some of the Democratic members of Congress from New York. In interviews, they generally praised Torres and Blake — who worked on Barack Obama's 2008 campaign and then in the White House — while noting others could also join the race. But the conversation turned sour when asked about Díaz Sr.

Rep. Adriano Espaillat said Torres is "one of the good candidates" and Blake is "also a worthy candidate." When asked about Díaz, Espaillat said, "We'll leave that one."

Ocasio-Cortez, who serves the neighboring district, said it was "unfortunate" that Díaz entered the race. "He has a disturbing track record towards the LGBT American community," Ocasio-Cortez told CNN. She said she would "absolutely not" support his candidacy. (Díaz has claimed he is the "opposite" of Ocasio-Cortez.)

Another member of the delegation said, "I don't think there's any real concern right now that he's guaranteed to win that race, but people are monitoring the situation."

To be sure, there will be other issues in the race besides Díaz's candidacy. Torres called for a congressional investigation into Trump administration's "almost willfully starving" of Puerto Rico. And he has straddled ideological lines, supporting Sen. Bernie Sanders in the 2016 presidential primary, without embracing that candidate's signature issues like single-payer health care or the Green New Deal. Torres calls himself a "pragmatic progressive" that wants to "maximize" renewable energy and supports "at a minimum" providing a public health insurance option. He notes all the hospitals in the area and says he wants to hear from the unions before considering more sweeping overhaul of the health care sector.

"The residents of the South Bronx are largely motivated by bread and butter concerns, a struggle to survive in the most expensive city in the world in a city that's becoming crushingly unaffordable," he said.

As for Blake, he's pitching a "believe in the Bronx" campaign, while trying to prove that he can win a race for Congress after losing a campaign for New York City Public Advocate in a special election earlier this year. He said the campaign raised his profile and he has plenty of time before the congressional primary.

"I already represent a Latino-majority district and been elected three times," Blake said. "People are looking for a vision, they're not just looking to you because of race."

"I think this is about people deciding who is the best representative for us, not just on ethnicity and background but truly who can unite," he added.

But on one thing, both agree: Rubén Díaz Sr. needs to go.