The president noted that lawmakers may lack the "appetite" to take on immigration while many of them are up for re-election and while another big legislative issue - climate change - is already on their plate.
"I don't want us to do something just for the sake of politics that doesn't solve the problem," Obama told reporters Wednesday night aboard Air Force One.
Immigration reform was an issue Obama promised Latino groups that he would take up in his first year in office. But several hard realities - a tanked economy, a crowded agenda, election-year politics and lack of political will - led to so much foot-dragging in Congress that, ultimately, Obama decided to set the issue aside.
With that move, the president calculated that an immigration bill would not prove as costly to his party two years from now, when he seeks re-election, than it would today, even though some immigration reformers warned that a delay could so discourage Democratic-leaning Latino voters that they would stay home from the polls in November.
Some Democrats thought pushing a bill through now might help their party, or at least their own re-election prospects.
Senate Majority Leader Harry Reid, whose campaign is struggling in heavily Hispanic Nevada, unveiled an outline - not legislation - on Thursday for an immigration bill at a packed news conference. Asked when it might advance, he declined to set an "arbitrary deadline."
If immigration goes nowhere this year, Democrats can blame Republican resistance, though in reality many Democrats didn't want to deal with an immigration bill this year either.
The Democrats' draft proposal, obtained by The Associated Press on Tuesday, called for, among other things, meeting border security benchmarks before anyone in the country illegally can become a legal permanent U.S. resident.
Obama praised the outline and said the next step is ironing out a bill. He said his administration will "play an active role" trying to get bipartisan supporters.
Republican Sens. Jon Kyl of Arizona and Lindsey Graham of South Carolina, who had been working with Democrats on immigration reform, criticized the proposal as "nothing more than an attempt to score political points."
By Wednesday, House Speaker Nancy Pelosi offered little hope that the issue was still alive on Capitol Hill.
"If there is going to be any movement in this regard, it will require presidential leadership, as well as an appetite, is that the word? ... as well as a willingness to move forward in the Congress," she said.
House Republican leader John Boehner was more blunt. "There is not a chance that immigration is going to move through the Congress," he said Tuesday.
Rep. Luis Gutierrez, the Democrats' leading advocate for immigration reform, has said he voted for health care reform on the understanding that Obama and congressional Democrats would move a major immigration bill.
Even though he would like to see Latinos turn out to vote for Democrats in 2010, Gutierrez said "many will probably decide to stay home." However, he added, a strict, new immigration law in Arizona may change that dynamic. The law requires law enforcement officers to question anyone they suspect is in the country illegally.
"On one hand you are not going to vote because you don't believe people you voted for are doing a good enough job," Gutierrez said. "Then you say, 'I got to vote, because the enemy is so mean and vindictive, I got to get out there.'"
The Hispanic vote is growing, largely because of Latinos' increasing population. The 9.7 million Latinos who cast ballots in 2008 made up about 7.4 percent of the electorate, according to a 2009 Pew Research Center study.
Hispanic voters helped flip the battleground states of Colorado, Florida, Nevada and New Mexico from Republican to Democratic in the 2008 presidential election.
But even though Latinos' numbers have been increasing, in some parts of the country their portions of voting populations are not large enough to affect election outcomes.
Democrats hold a 254-177 majority in the House, with four vacancies. But 48 are in districts where Republican Arizona Sen. John McCain did better than Obama in the 2008 elections.
Matt Angle, a Democratic political strategist focused on Texas, said it would be worse for Democrats to propose a bill that has no hope of passing or getting Republican support. Doing so would allow Republicans to cherry-pick parts of the bill to use against Democratic candidates, he said.
The Senate also has a number of competitive races, some in states with significant numbers of Hispanic voters, such as in Nevada, Reid's home state. Latinos are about 12-15 percent of likely voters there.
"For Democrats it is critical they can deliver if they want to continue nurturing the support they want from this community," said Clarissa Martinez De Castro, National Council of La Raza immigration and national campaigns director.