Republican U.S. Presidential nominee Donald Trump attends a campaign event at Briar Woods High School in Ashburn, Virginia, August 2, 2016.
Republican U.S. Presidential nominee Donald Trump attends a campaign event at Briar Woods High School in Ashburn, Virginia, August 2, 2016.

WASHINGTON - Donald Trump's week-long feud with Khizr and Ghazala Khan, the Muslim parents of a U.S. soldier killed in Iraq, is leading more fellow Republicans to publicly criticize the candidate, highlighting lingering tensions with top party leaders.

Meg Whitman, a prominent technology executive who launched an unsuccessful bid for the California governorship in 2010, told The New York Times late Tuesday that she will support and raise money for Democratic presidential nominee Hillary Clinton, calling Trump “a dishonest demagogue.” And U.S. Representative Richard Hanna of New York became the first sitting Republican member of Congress to throw his support to Clinton, saying he was “incensed” by the Republican nominee’s comments about the Khans.

FILE - Margaret (Meg) Whitman, shown in 2014, lead
FILE - Margaret (Meg) Whitman.

The endorsements came hours after President Barack Obama took the unprecedented step of a sitting U.S. leader denouncing a presidential candidate, when he called Trump “unfit to serve” as the nation’s commander-in-chief.

Trump swiftly responded to Obama’s comments, saying it is almost an “honor” to be criticized by him, adding that Obama does not know what he is doing and calling him a “weak president.”

The controversy began after Khizr Khan, the slain soldier’s father, denounced Trump over the Republican nominee's proposal to bar foreign Muslims from coming to the United States. Khan said this would have prevented his son from joining the U.S. military.

Khizr Khan, who's son Humayun was killed serving i
Khizr Khan, who's son Humayun was killed serving in the U.S. Army ten years after September 11, 2001, challenges Republican presidential nominee Donald Trump to read his copy of the U.S. Constitution at the Democratic National Convention in Philadelphia,

Trump responded by belittling the family, suggesting that the mother did not speak at the convention because she was not “allowed” to do so. Trump continues to insist his criticisms are valid and the news media have portrayed him unfairly.

Leading Republicans have said that regardless of political views, the parents of slain U.S. soldiers must be treated with respect by political leaders.

Presidential historian Allan Lichtman of American University told VOA that Obama’s assessment of Trump is unprecedented. “I cannot recall a sitting president who has called an opposition candidate “unfit” to serve in modern history.”

Lichtman said he has often heard sitting presidents criticize opposition political candidates, but cannot remember any other candidate being labeled “unfit” or unprepared to serve.

Obama, who has endorsed Democrat Hillary Clinton as his successor when he leaves office in January, challenged Republicans to repudiate Trump, saying his complaints against Khizr Khan and his wife Ghazala after they endorsed Clinton at last week's Democratic National Convention were offensive.

Obama said several leading Republicans have denounced any insults of the Khan family, but he said that is not enough. “There has to be a point in which you say, this is not somebody I can support for president of the United States, even if he purports to be a member of my party. And the fact that that has not yet happened makes some of these denunciations ring hollow.”

In an interview with VOA’s Urdu service Monday, Khizr Khan said some good has already come out the political firestorm with Trump.

"It really has come out. It really, really has come out that a significant larger number of Republicans are asking him to tone down, change those derogatory remarks about minorities, not only just Muslims, but other minorities," Khan said.

WATCH: Khizir and Ghazala Khan Talk to VOA

Rifts with Republicans

Trump told The Washington Post in an interview Tuesday that he will not endorse House Speaker Paul Ryan or Arizona Senator John McCain in their re-election bids. Ryan and McCain have both endorsed Trump but also publicly rebuked him over his criticism of the Khans.

Another controversy erupted Tuesday when Trump accepted a Purple Heart medal from a retired lieutenant colonel before a rally in Ashburn, Virginia. Trump said the former soldier told him the gesture was intended to show confidence in him.

Republican U.S. Presidential nominee Donald Trump
Republican U.S. Presidential nominee Donald Trump talks to Lt. Col. Louis Dorfman, who gave Trump his Purple Heart, during a campaign event at Briar Woods High School in Ashburn, Virginia, Aug. 2, 2016.

The Purple Heart is given to a U.S. serviceman or woman wounded in combat, or posthumously given to someone killed in battle. It is a sacred U.S. military tradition.

Trump, who has expressed regret for never serving in the military, said he was honored by the soldier's gift. The audience chuckled when he said he had "always wanted to get the Purple Heart. This was much easier."

A spokesman for the Military Order of the Purple Heart organization, John Bircher, was not amused.

"It is absolutely horrible for anyone to wear or have the Purple Heart medal who is not entitled to it," Bircher told CBS News. "Donald Trump did not get the Purple Heart and there's no 'easy way' to get it. I don't think he has any clue as to the meaning of the Purple Heart medal."

Meanwhile, another controversy will continue to dog Trump through the campaign season. Federal judge Gonzalo Curiel has rejected a request by Trump’s attorneys to dismiss a lawsuit against the billionaire, accusing him of defrauding students who had enrolled in his real-estate investing school, Trump University. Back in May, Trump accused Curiel of being unable to fairly preside over the case because of Trump's campaign pledge to build a wall along the U.S.-Mexican border. Curiel is a U.S.-born citizen of Mexican descent.

The election is still three months away, but attention to the controversies has distracted from discussion of Trump's policy proposals and to a certain extent Democratic candidate Hillary Clinton's as well. The time they each spend answering questions about Trump's comments takes away from opportunities to tell more voters what they would do if elected.

Opinion polls

Recent public opinion polls indicate voters are viewing Clinton more favorably in the aftermath of last week's national party convention, even as they continue to question her honesty and trustworthiness.

Hillary Clinton delivers her acceptance speech at
Hillary Clinton delivers her acceptance speech at the Democratic National Convention in Philadelphia, Pennsylvania, July 29, 2016. (Photo: A. Shaker / VOA)

The latest CNN/ORC poll showed the former U.S. secretary of state with an edge over Trump on who would better handle several public policy issues, including the economy, immigration, health care and fighting Islamic State terrorists. Clinton gained ground on all four issues over Trump from the last poll conducted by the cable news channel.

CNN said Clinton has pulled even with Trump on who would be best at handling terrorism and holds a marked edge over him on setting U.S. foreign policy.

A CBS News poll shows Clinton with a significant edge over Trump on the question of which candidate is better prepared to be president. The survey showed voters believe Clinton, by a 60 percent to 37 percent margin, is prepared, while only 35 percent say Trump is prepared and 61 percent said that he is not. The CBS poll said 57 percent believe Clinton has the right temperament and personality to be president, but only 31 percent agreed that Trump does.

Clinton's campaign continues to be weakened by perceptions that she is less than honest and trustworthy, although surveys have shown that Trump also fares poorly on the same question. The CBS poll said 34 percent of voters it surveyed viewed Clinton as honest, while 60 percent did not. Trump had a 36 percent favorable rating on honesty, 59 percent negative.