By Lisa Desjardins, CNN Radio Senior Correspondent
Washington (CNN) - Few might realize it, but Tuesday's primary elections might have quietly sealed the racial and ethnic makeup of the U.S. Senate for a couple of more years.
On Tuesday, C. Anthony Muse, thought to be the strongest black candidate for U.S. Senate this year, lost his Democratic primary race in Maryland, coming in a distant second to Sen. Ben Cardin, the incumbent. CNN found only one other African-American on a Senate ballot, a Florida candidate who isn’t getting much attention among a wide field of contenders.
Out of 100 U.S. senators, two are Latino, two are of Asian or Pacific Islander ancestry, but none are African-American. Tuesday's primary losses mean a Senate body with relatively little racial or ethnic diversity will likely continue to have no black members for two more years.
"When I tell this to people, most of them are shocked and don't understand how in America that could be the case," said Muse, a Maryland state senator and preacher.
There have been 1,931 members of the Senate, the chamber historian's office said. Six African-Americans have served in the U.S. Senate, Muse said, and that includes Roland Burris of Illinois, who was appointed to President Barack Obama's former seat and served less than a full term.
Six Latinos have held the title of U.S. senator.
"There does seem to be a ceiling," University of Mississippi political science professor Marvin King said. "People are used to electing minority office holders. There are plenty of blacks in every state legislature, but going beyond that to winning statewide races seems to be a ceiling."
Part of it might be simple math. Minorities, by definition, represent less than the majority of a population.
The same math might be affecting how African-Americans in the House of Representatives transition to the Senate, too. There are currently 44 black House members, a record-high number.
"How come minority members of the House have not transitioned to the Senate the way you see white members transition?" King asked. "One of the answers is the districts they represent tend to be different from the state as a whole. They tend to represent urban districts with high minority populations."
Conservatives, such as Cuban-American Sen. Marco Rubio, R-Florida, see the lack of minority representation as a straightforward reflection of who's on the ballot and whom voters chose.
"We have elections in this country," Rubio said. "Obviously, we'd like to see more people running for all offices in this country. I don't know why it's been the way it's worked out. I think that will change over time."
Most senators who were asked about the low number of minorities in the Senate admitted or implied the issue was not something on which they focused.
Sen. Bill Nelson, D-Florida, whose state is embroiled in discussions about race after the death of teenager Trayvon Martin, didn't have an answer when asked about the lack of diversity.
"Minorities in the Senate?" he asked. "Call the office and we'll talk about that, because that deserves a thoughtful answer."
His office later sent a written reply that the senator believes "the Senate would benefit from more closely resembling America's diversity." His aide theorized that Nelson was probably in a hurry to get to his next meeting and that's why he could not answer on the spot.
The lack of specific responses from across the Senate didn't surprise Sen. Bob Menendez, D-New Jersey, the other Latino in the chamber.
Diversity in the Senate is "not at all" a discussion among members, he said.
"I don't think they think about it necessarily," Menendez said. "It's not as if they're averse to being helpful or supportive, but they're not thinking about it."
So does it even matter if the Senate has low numbers of minorities?
King, the University of Mississippi professor, said the effect might be more indirect than direct.
"My research has found that on all but a handful of issues in Congress ... the voting of black Democrats and white liberals is nearly identical," he said. The issues where he sees separation are housing, urban development and civil rights.
King and other researchers said they believe the effect of low minority representation is less on votes taken than issues presented.
"Where you might see a difference is in the agenda of the individual members of Congress, what bills they chose to introduce and where they put their energy," he said.
Before he lost his U.S. Senate primary race, candidate Muse gave a list of issues he felt were overlooked, including infant mortality, the criminal incarceration rate, housing and urban health care.
Now he's returning to the Maryland state Senate, vowing that he will keep pushing for a seat in Washington.