President Obama discussed the ongoing investigations into allegations against the Department of Veterans Affairs at a news conference on Wednesday, following his meeting with Sec. Eric Shinseki and White House Deputy Chief of Staff Rob Nabors. (Sarah Parnass/The Washington Post)

One of President Obama’s top aides is being dispatched to Phoenix this week to investigate deaths allegedly connected to a Department of Veterans Affairs medical center there, part of the administration’s efforts to contain growing outrage over delays in treatment and accusations of rigged recordkeeping at veterans hospitals.

Rob Nabors, a White House deputy chief of staff, has been assigned to assist top VA officials in probing allegations of wrong­doing by staffers at the Phoenix facility and elsewhere, the White House said Tuesday. He will be meeting with Arizona hospital officials Thursday after gathering Wednesday with representatives from several veterans groups in Washington, officials said.

Republicans have seized on the VA allegations as potential fodder for this fall’s midterm elections, and several GOP senators have called for the resignation of Veterans Affairs Secretary Eric K. Shinseki.

The department’s top health official, Robert Petzel, resigned last week under pressure from Shinseki. White House press secretary Jay Carney said Obama “has confidence” in Shinseki and will wait for the results of an internal review at VA before taking further action.

The controversy is particularly acute for Obama, who has joined with first lady Michelle Obama and Jill Biden, the wife of his vice president, in focusing on veterans’ issues. The White House has pressed successfully for more federal funding for VA, expanded the list of what qualifies for disability treatment and urged private sector firms to employ veterans once they return from Iraq and Afghanistan.

Obama’s heavy focus on veterans’ care came in the wake of the George W. Bush administration-era scandal at what was then Walter Reed Army Medical Center, a Defense Department facility that was shuttered following Washington Post reports of patient neglect and shocking living conditions.

In an interview Tuesday, White House Chief of Staff Denis McDonough said the administration welcomes “the oversight and tough questioning” it has received on the recent VA allegations. McDonough will meet with Senate Veterans’ Affairs Committee Chairman Bernard Sanders (I-Vt.) Wednesday to discuss the matter, aides said.

“We will dig in to find out exactly what those allegations are, whether they reflect a systemic challenge, whether they reflect a series of isolated challenges, and we will address them in either case,” McDonough said.

Veterans Affairs’ inspector general is looking into allegations by a former Phoenix clinic director that up to 40 veterans died while waiting for treatment at a VA hospital while staffers disguised the wait times that patients faced. The inspector general told a Senate hearing last week that his initial probe has found no evidence that delays caused the deaths. Shinseki is conducting his own review with the help of Nabors.

A handful of Republicans, including Sens. John Cornyn (Tex.) and Jerry Moran (Kan.), have called for Shinseki’s ouster, and other GOP lawmakers are questioning the administration’s response to the allegations.

House Majority Leader Eric Cantor (R-Va.) said Tuesday that he was “disturbed” by reports suggesting that Obama first learned of the allegations against Veterans Affairs through news reports. “It is time for our president to come forward and take responsibility for this and do the right thing by these veterans and begin to show that he actually cares about getting it straight,” Cantor said.

House Veterans’ Affairs Committee Chairman Jeff Miller (R-Fla.) also complained Tuesday about VA’s response to a committee subpoena, saying the department provided copies of only about 200 e-mails from one senior official. He said the response “makes me suspicious that the department has something to hide.”

Rep. Tammy Duckworth (D-Ill.) — an Iraq war veteran, double amputee and former VA assistant secretary — said in an interview that the allegations are similar to problems she faced at the department from 2009 to 2011. “I’m not surprised, because it’s such a large network that you’re going to find problems,” Duckworth said. But she expressed support for Shinseki and said he should not resign. “I think he should fix it,” she said. “I’m not trying to put words in his mouth here, but I would think that he would want to fix it.”

When asked whether the allegations could affect Obama’s legacy of helping the nation’s veterans, Duckworth took a long pause before answering.

“It’s hard, because Mrs. Obama has done so much and Mrs. Biden has done so much, and I see that as part of the president’s push,” she said. “I think he’s relied on Secretary Shinseki, but we could use his personal attention at this point.”

Obama said at a news conference last month that he took the VA allegations “very seriously.” When asked about Duckworth’s comments Tuesday, Carney said, “The personal attention is there.”

The Phoenix VA allegations were first reported by the Arizona Republic newspaper last month.

Cornyn said Tuesday that Obama should withdraw the nomination of Jeffrey Murawsky to serve as the new VA undersecretary for veterans health. “Instead of nominating a reformer from outside the VA system,” Cornyn said, Obama opted to nominate a “career administrator” from within the department’s ranks.

Sanders said politicization of the issue would be “unconscionable.” He said representatives of service organizations who testified before his panel last week agreed that VA continues to provide quality health care.

McDonough said that a chronic backlog of veterans’ disability claims at VA had been cut in half over the past year and that funding for the VA health system has increased 38 percent under Obama. But he said the VA network has been strained by new policies attempting to get more veterans into the system, including streamlining disability claims for those exposed to Agent Orange during the Vietnam War or suffering from post-traumatic stress disorder after serving in Iraq and Afghanistan.

McDonough said participation in the VA health system has gone up 16 percent since 2008.

Veterans who served in Iraq or Afghanistan after 9/11 gave a mixed review of the agency in a Washington Post­Kaiser Family Foundation poll conducted last year. Fifty-eight percent of respondents said VA is doing an “only fair” or “poor” job of meeting the needs of veterans, while 38 percent described the job VA is doing as “excellent” or “good.”

Of veterans who use VA for health coverage, however, 82 percent said their overall physical health needs were being met “very” or “somewhat” well, compared with 17 percent who said they were not being met well.

On Wednesday, House lawmakers are expected to approve the VA Management Accountability Act, a bill sponsored by Miller that would make it easier to fire any “poorly performing” senior VA employees and managers.

Miller and his colleagues wrote the bill in response to a year-long committee investigation that found at least 20 “preventable veteran deaths” in the VA system. The probe also determined that more than 50 veterans were seriously harmed by delays in endoscopies and other procedures in Georgia, Pennsylvania, Tennessee and other states. The majority of the deaths occurred in 2010 and 2011, according to the report.

Some Democrats have become more vocal in expressing disappointment with the Obama administration’s handling of veterans issues. In Michigan, Rep. Gary Peters, who is running for the state’s open U.S. Senate seat, wrote in a letter to Shinseki on Monday that ensuring that veterans are receiving proper medical care is “the most pressing and immediate issue.”

“We’ve got to get to the point where we don’t need a congressional or senatorial office to help you get into the system,” Peters said in an interview. “It’s got to work seamlessly for our veterans.”

Scott Clement and Peyton M. Craighill contributed to this report.