Donald Trump’s assertion this week that the November elections might be “rigged” against him is “ridiculous,” President Obama said Thursday.

Noting that elections are conducted by 50 states and not by the federal government, Obama said during a news conference at the Pentagon that he was somewhat dumbfounded about how to react to Trump’s comments. “That does not make any sense and I don't think anybody would take that seriously,” he said.

The GOP nominee should “get out there and try to win the election,” Obama continued. “If Mr. Trump is up 10 or 15 points on Election Day and ends up losing, you know, maybe he can raise some questions. That doesn't seem to be the case at the moment.”

The president, who celebrated his 55th birthday Thursday and departed the Pentagon to attend a birthday dinner at an elegant restaurant in Georgetown, was referring to multiple new polls this week that found Hillary Clinton ahead of Trump nationally and in key battleground states, in some cases by double digits.

Most pollsters believe the Democratic nominee’s August lead is a reflection of a strong Democratic National Convention program in Philadelphia, combined with public disapproval of Trump’s comments about the Muslim-American parents of an Army captain killed in Iraq in 2004. Republican lawmakers and Trump campaign advisers have advised the GOP nominee to focus his ire on Clinton and her policies, rather than upbraiding Gold Star parents who lost a child.

Obama, asked if he felt qualms about the administration’s obligation to brief Trump as a nominee about classified national security information, said he would follow the law, but warned that seeking to become president demands acting like one.

“And that means being able to, you know, receive these briefings and not spread them around.” Obama said he would not describe what kinds of information Trump and Clinton can access.

Pundits and analysts have questioned whether Trump, who speaks during rallies and interviews about anything he has read, heard or imagined, lacks the self-discipline to keep classified information under wraps. Republicans, on the other hand, have said Clinton should not be given the green light to receive classified information because of what the FBI called her “extremely careless” handling of classified emailed material while she was secretary of state.

Obama made his deep misgivings about Trump clear when asked if he trusted Trump to control the country’s arsenal of nuclear weapons.

“Just listen to what Mr. Trump has to say and make your own judgment with respect to how confident you feel about his ability to manage things like our nuclear triad,” Obama told reporters during an hour-long news conference that followed a two-hour national security meeting at the Pentagon.

“What I can say is, this is serious business and the person who is in the Oval Office and who our secretary of defense and our joint chiefs of staff and our outstanding men and women in uniform report to, you know, they are counting on somebody who has the temperament and good judgment to be able to make decisions to make America safe,” Obama said as Defense Secretary Ashton Carter looked on from the side of the room.

“And that should be very much on the minds of voters when they go in the voting booth in November.”

Obama defended the administration's delivery of a $400 million cash payment to Iran in January, arguing the funds were claimed as Iran’s in a dispute dating to 1979 and were announced publicly at the time the international nuclear deal was reached last year.

The cash transfer was neither “nefarious,” nor was it ransom paid for the release of four American hostages, he said, rejecting speculation and criticism raised by some Republicans. “We do not pay ransom … because if we did we would be encouraging Americans to be targeted,” he said. The president called the controversy “the manufacturing of outrage” about an agreement with Iran that was never secret. “It’s interesting to me how this became a story again,” he added.

In response to a reporter's question about Trump's temperament, Obama said he would not repeat his withering assessments of the mercurial candidate on Tuesday, when he declared Trump “unfit” and “woefully unprepared” to be president.

“I have offered my opinion, but ultimately, it is the American people's decision to make collectively,” Obama said of the choice. “And if someone wins the election and they are president, then my constitutional responsibility is to peacefully transfer power to that individual and do everything I can to help them succeed.”

Obama on Thursday convened a periodic update with his advisers focused on ISIL, also known as ISIS, working through evidence of progress and setbacks in Iraq and Syria, and elsewhere where the terror group has expanded its reach. The president is set to vacation in Martha’s Vineyard with his family beginning Saturday and will not return to Washington for several weeks. He said the trip across the Potomac River to the Defense Department might be the last of his presidency.

In addition to Carter, Obama’s meeting included Vice President Joe Biden; Secretary of State John Kerry; Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff; James Clapper, director of national intelligence; John Brennan, director of the CIA; and 25 additional officials, including Cabinet secretaries and senior advisers, according to the White House.

The global battle against ISIS -- and its adherents living in Europe and the United States -- will pass to Obama’s successor next year. The president is aware that while his job approval numbers have edged above 50 percent in recent polls, he earns lower marks from the public for his handling of terrorism and national security.

Obama strode into the Pentagon briefing room eager to help edit history’s account of the bloody rise of the Islamic State in Iraq and Syria, which occurred on his watch and forced him to maintain higher numbers of U.S. troops in Iraq and Afghanistan, engage in endless bombing strikes from the air, and deploy special forces into Syria.

“I want to repeat, ISIL has not had a major successful offensive operation in either Syria or Iraq in a full year,” Obama said. “Even ISIL's leaders know they're going to keep losing. In their message to followers, they're increasingly acknowledging that they may lose Mosul and Raqqah -- and ISIL is right. They will lose them. And we'll keep hitting them and pushing them back and driving them out until they do.”