WASHINGTON: President Obama’s plan to start work on immigration reform - reaffirmed by White House staff last week - launched two sharply different views on how it will impact his domestic agenda.

Supporters applaud Mr. Obama’s holistic approach, arguing that all the interrelated issues of the economy, healthcare, and homeland security must be dealt with together.

But to others, immigration reform is one of the most divisive issues in American politics — a

“poison pill” that could sour the mood in Congress and clip the president’s momentum.

By adding it to his “to do” list, Obama is putting lawmakers on both sides of the aisle in a bind, forcing them into votes that can then be wielded against them on the campaign trail.

“Democrats have to worry about offending Latino voters — that would create problems in primaries,” says John Pitney, a political scientist at Claremont McKenna College in Claremont, Calif. “Republicans have to deal with the enforcement-only folks, also in primaries.”

The last bid for comprehensive reform legislation derailed in the Senate in June 2007. Republicans who were willing to support then-President Bush on immigration aren’t as likely to take political risks for a Democratic president. “If Republicans have learned nothing else, it’s that their primary electorates don’t look kindly on anything that looks like amnesty,” says Mr. Pitney.

The immigration issue poses special problems for each party. Since 2007, elements of the issue have come back as amendments to certain bills working their way through Congress. Members of Congress have called them “poison pills,” because they aim to force legislators to record their votes on divisive issues.

On the House side, a tax bill included a vote on whether to require the Internal Revenue Service

to toughen enforcement against illegal immigrants, including denial of the earned income tax credit. The April 15, 2008, vote split the House, 210 to 210. The Senate never took up the bill.

Immigration is so divisive that opponents of other issues - ranging from annual spending bills to healthcare reform - have tried to bring immigration into the discussion as a way to fracture the support for bills.