Months after ending his brief vanity run at the Republican presidential nomination, Donald Trump is still striving to inject himself into the presidential election. Reuters

Months after ending his brief vanity run at the Republican presidential nomination, business mogul Donald Trump is still striving to inject himself into the presidential election.

The real estate titan's latest bid for attention came with his declaration on Monday on Fox News, when Trump ominously referenced a bombshell he is set to drop later in the week -- a piece of information, he implied, that will reflect poorly on President Barack Obama.

"I have something very, very big concerning the president of the United States," Trump said. "It's very big, bigger than anyone would know."

We've been here before. Earlier this year, conservative provocateur Andrew Breitbart, who has since died, breathlessly built up the expectation for an incriminating video that turned out to be a much younger Obama, then a student at Harvard Law School, speaking at a rally in favor of greater faculty diversity.

So don't count on Trump changing the course of the election. Then again, such things have happened before: last-minute developments that help sway the outcome. Here is a list of some of the more famous ones:

Nixon's secret plan: In 1968, Richard Nixon said he had a blueprint to extricate the United States from its increasingly unpopular war in Vietnam. Nixon's so-called "secret plan" to end the war -- a phrase coined by a reporter but never disavowed by Nixon -- helped him win the presidency, but his supposed route out of Vietnam did not materialize. In fact, he prolonged and expanded the conflict.

Iran hostages: The 1980 election was dominated by the 52 Americans being held in captivity in Iran after the Islamic revolution that overthrew the U.S-backed regime of the Shah. President Jimmy Carter's attempts to free the hostages prior to the election foundered, helping Ronald Reagan win in November. Critics charged afterward that Reagan and his running mate, George H.W. Bush, had struck a deal to delay the hostages' release until after the presidential contest, allegations that have never been confirmed.

Iran-Contra: Shortly before the 1992 presidential election, Caspar Weinberger, who served as Reagan's secretary of defense, was indicted for his alleged involvement in the Iran-Contra affair, a scandal in which officials sold weapons to Iran, despite an arms embargo, to help fund anti-government rebels in Nicaragua. President George H.W. Bush pardoned Weinberger after losing the election.

Bush drunk driving: Just days before the 2000 election, a reporter confirmed that George W. Bush had been arrested in 1976 for driving under the influence in Maine. The episode came during Bush's wilder days, before he found religion and gave up drinking, and the Texas governor ended up winning the presidency in a contentious, razor-thin election.

Osama bin Laden video: It may seem hard to remember given how little foreign policy has played a role in this election, but the Bush administration's "War on Terror" -- particularly the decision to invade Iraq -- was the pivot on which the 2004 election swung. Bush argued against changing commanders-in-chief in the midst of a conflict. A few weeks before the election, Al-Jazeera aired a video of Osama bin Laden claiming responsibility for the attacks of Sept. 11, 2001 and warning that "your security does not lie in the hands of Kerry, Bush or al Qaeda." The American people disagreed, deciding to give Bush another four years of control over military decisions.