Missile defense isn't the only area in which President Barack Obama will have "more flexibility" if he's re-elected. Immigration, the Canada-to-Texas oil pipeline, gay marriage, tax policy and other issues could invite bold initiatives by a president who knows he will never run for office again, especially if his party gains ground in congressional elections.
For now, however, Obama is postponing action on several difficult issues, knowing that Republicans are determined to deny him political victories a few months before their chance to oust him. He's hardly the first to adopt that strategy.
Obama expressed a fundamental truth when he quietly told Russia's president that he will have "more flexibility" to deal with the touchy issue of missile defense after the Nov. 6 election _ if Obama wins, that is. The statement might have raised few eyebrows had Obama made it nonchalantly to a U.S. audience. Instead, it kicked up a fuss because Obama thought the microphones were off when he spoke with Dmitry Medvedev in South Korea, and because Obama seemed to take his re-election for granted.
Presidents traditionally ease their foot from the gas pedal in their fourth year, when re-election politics overshadow almost everything.
President Bill Clinton, a Democrat, played small-ball in 1996, proposing school uniforms and midnight basketball programs after previously tackling much tougher issues such as welfare cuts and targeted tax increases (successfully) and a major health care overhaul (unsuccessfully).
President George W. Bush, a Republican, talked vaguely of overhauling Social Security during his 2004 re-election campaign, and then found the public wasn't ready for major changes after he won. Had he emphasized the proposed revisions during his campaign, Democrats' cries of "privatization" might have tipped the close election to Massachusetts Sen. John Kerry.
"No president of either party has any flexibility whatsoever during a re-election year," said Dan Schnur, a former GOP presidential aide who teaches political science at the University of Southern California.
"Your honeymoon is long gone," he said. "Everything you do will be judged strictly in a political context. And anything you do that's remotely unpopular could cost you the election."
Obama has been blunt about election-year constraints. At a March 6 news conference, he acknowledged Hispanic supporters' anger over his failure to achieve immigration changes, including paths to legal status for some illegal immigrants.
"When I came into office, I said, `I am going to push to get this done,'" Obama said. "We didn't get it done. And the reason we haven't gotten it done is because what used to be a bipartisan agreement that we should fix this ended up becoming a partisan issue."
Obama, foreshadowing what he told Medvedev, said a presidential election can change the policy landscape.
"My hope is that, after this election, the Latino community will have sent a strong message that they want a bipartisan effort to pass comprehensive immigration reform," he told reporters.
Obama also failed to deliver on his 2008 campaign promise to undo the Bush-era tax cuts for the wealthy. The president postponed action in late 2010, when high unemployment made tax increases harder to defend.
Now the Bush-era tax cuts for everyone are set to expire shortly after the November election unless Congress acts. The agreement was part of a bipartisan compromise last fall in which Obama forced Republicans to agree to no more debt-ceiling showdowns until after the election.
Obama has had a shakier time slow-walking the proposed Keystone XL pipeline, which would carry oil from Canada to the Gulf Coast. Environmental groups strongly oppose the plan, but Obama's GOP opponents hammer him almost daily for not approving it.
The president has struggled to finesse the issue. He recently directed the government to fast-track an Oklahoma pipeline while saying congressional Republicans refused to allow sufficient time to review the larger Keystone project. Republicans scoff at the claim.
On another front, many activists believe Obama will endorse same-sex marriage if he wins a second term; the White House has not promised to do so.
Presidents typically push hard for achievements in their first three years, show more caution in their fourth year and then aim high again if they win re-election.
Clinton tackled health care, tax increases on the rich, the North American Free Trade Agreement and welfare revisions in his first term.
Bush sharply cut taxes, twice, as the budget surplus was changing to a deficit. Obama led a brutally partisan fight for the health care overhaul now before the Supreme Court.
Will Obama boldly push for big changes in immigration, Social Security or other difficult issues if he wins a second term?
Recent history offers few hints. The last four presidents to win re-election saw their second terms bog down in scandals or controversies: Richard Nixon and Watergate; Ronald Reagan and Iran-Contra; Clinton and intern Monica Lewinsky; Bush and Hurricane Katrina and the increasingly unpopular Iraq war.
Nothing illustrates the dilemma facing a fourth-year president better than Bush's handling of Social Security.
After narrowly defeating Kerry in 2004, Bush announced: "I earned capital in the campaign, political capital, and now I intend to spend it."
In his autobiography, "Decision Points," Bush wrote, "For someone looking to take on big issues, it didn't' get much bigger than reforming Social Security." He said he "embarked on a series of trips to raise awareness about Social Security's problems and rally the American people to insist on change."
Such a call to arms, of course, often takes place in an election campaign, not after it. Bush's bid to allow partial privatization of Social Security for younger workers quickly collapsed in the face of strong Democratic opposition and tepid GOP support.
"I may have misread the electoral mandate by pushing for an issue on which there had been little bipartisan agreement in the first place," Bush wrote. "The failure of Social Security reform shows the limits of the president's power."
Obama may have "more flexibility" to deal with missile defense, immigration and other issues if he wins a second term. Whether he will have a mandate to do so is another question.