Hope over prospects for immigration reform, a bipartisan glow unheard of in polarized Washington, has for now suppressed political wildcards that could yet blunt the ambitious effort.

President Barack Obama and top Republicans are for once in agreement that political and demographic trends have suddenly shifted to offer the best chance for serious reform in a generation.

"Rare is the time that Washington DC moves faster than expected," said Ali Noorani, Executive Director of the National Immigration Forum.

"Now, the question is not so much as to when the process will begin -- but how quickly the process is moving."

Obama laid out his approach to bringing 11 million illegal immigrants out of the shadows in Nevada on Tuesday, a day after a bipartisan coalition of senators proposed a similar approach to new laws.

Top players agree that there is an opening now, because after Obama drubbed Mitt Romney among Hispanics in November, Republicans cannot risk entering another election, in 2016, alienating that key voting block.

Hispanics made up a record 10 percent of the electorate, and 71 percent went for Obama, who touted immigration reform, while Romney opposed it.

Another reason why reform may happen now is the president himself -- Obama wants a big win to match his historic health care reform law in his first term.

Other top ticket items, like gun control, global warming, and big debt and spending compromises appear elusive, so Obama has every incentive to stake everything on immigration reform.

But just because logic backs reform that does not mean that Congress, boiling with political bile, will do what seems to make sense.

Details are scarce of both current plans and some issues that scuppered the last effort, in George W. Bush's second term, in 2007, remain unresolved.

For instance, the Senate plan makes an eventual path to citizenship for illegal immigrants "contingent" on specified actions to tighten border security and visa enforcement. Guest worker programs also remain divisive.

Obama's plan does not include an enforcement link, on grounds that it could result in an unrealistic timeframe for illegal immigrants to become citizens, perhaps even longer than expected lifespans.

But Republicans may need such a mechanism to appease conservatives fixated on border security but opposed to anything that smacks of "amnesty" for illegal immigrants.

Advocates suggest creative congressional language could bridge the gap and Obama aides point out that the enforcement issue may lack previous potency, after the deployment of more border police and inspections in recent years.

Obama warned Tuesday the debate would soon become "emotional" and, mindful that his toxic image among conservatives could make it hard for Republicans to compromise, has yet to play a role in framing the compromise.

He also knows current good feeling is perishable and that a second term president's authority soon wanes.

"We can't allow immigration reform to get bogged down in an endless debate," Obama said Tuesday, promising he would send his own bill and demand a vote if Congress tarried.

The politics however remains dicey for Republicans -- a factor reflected in plaudits being poured on Cuban American Tea Party favorite Senator Marco Rubio, who is taking big risks to lead his party on the debate.

Rubio, as a possible 2016 presidential candidate, has incentives to court Hispanic voters. But he also needs the support of hard core conservatives who vehemently oppose reform and vote in primaries.

"He couldn't be a better spokesman for this issue right now on the right side of the aisle," said Brad Bailey, CEO of the Texas Immigration Solution.

"We have got a lot of people in our party that are open to immigration solutions rather than immigration rhetoric."

The House of Representatives could also be a problem as conservative lawmakers up for re-election in 2014 may shirk from a dangerous vote.

A CBS poll this week found that while 51 percent of Americans now back allowing illegals a path to citizenship, only 35 percent of Republicans agree.

For now, White House officials, surprised and encouraged by the momentum, are more interested in highlighting opportunities than roadblocks.

And Rubio's intervention seems to have influenced some key conservative talk show hosts, who were instrumental in stopping reform in 2007 but are not foaming this time around.

Outside advocates also argue that the debate is different now.

"Some voices will point out the ways we could fall short of these goals," said Noorani.

But, he added "this is not the 2007 immigration debate."