Considering the difficulties facing any immigration-reform proposal, last week’s opening moves were encouraging.

A bipartisan group of eight senators released an outline of basic principles: tougher border security, a guest-worker program, a path to legal status for the 11 million undocumented workers now in the country.

President Barack Obama followed with a statement generally in line with those ideas — with the notable omission of a guest-worker program.

The problem Obama faces on that score is opposition from organized labor. Recall that when Obama was a senator, he helped torpedo a guest-worker provision in the unsuccessful reform bill pushed by then-President George W. Bush.

Both parties are divided on this issue, but Republicans more so than Democrats. It is far from clear enough GOP votes can be rounded up for comprehensive reform, especially in the House.

A key factor in the coming weeks will be Obama’s role. So far, he’s avoided wading into specifics, allowing the eight senators to proceed — a welcome sign he may be more interested in getting a bill passed than in acquiring an issue to use against the GOP.

Still to be determined: whether Obama — and the Democrats — will press for a too-easy path to legal status for undocumented workers, which would eviscerate GOP support, and whether Obama can agree to a guest-worker program despite labor’s opposition.

A guest-worker policy is an important element, one that recognizes that immigrants are essential in many seasonal industries such as agriculture. Without such a program, many immigrants feel compelled to settle and stay, knowing that if they go home when the work is done — as many did under the “Bracero” guest-worker program ended in the 1960s — they may be unable to return to the U.S.

The Republican presidential primary debates, with their loose talk of electrified fences and policies encouraging immigrants to “self-deport,” contributed to a psychologically crushing election defeat in November. Many Hispanics — and Asians — saw the GOP as thoroughly anti-immigrant.

Republican support for immigration reform won’t guarantee more Hispanic votes, but outright resistance would harden attitudes among such voters for years.

But Republicans shouldn’t back reform solely for political reasons. They should support it because it’s solidly in the national interest.

While too-rapid immigration can cause real problems, over the long term it is an undeniable benefit. The immigrant contribution in high-tech has been spectacular: Google, eBay and Intel were founded by immigrants or their children. Immigrants started more than half of Silicon Valley tech firms, according to a 2009 Kauffman Foundation study.

Meanwhile, the landscape has shifted dramatically since the unsuccessful reform effort of 2007. Last spring, a Pew report concluded that migration from Mexico had hit net zero and “may have reversed.”

“We have turned the page in terms of migration,” Roberto Suro of the University of Southern California told The Wall Street Journal. “We haven’t turned the page yet in terms of the policies.”

The need for successful reform is especially timely, in light of the sudden drop in U.S. fertility after the credit-market panic in ’08. This could be either a temporary blip or an ominous portent.

With the baby-boom generation retiring, demographic decline threatens slower growth, a heavier tax burden for a shrinking workforce — and a nation more inward-looking. As Harvard’s Joseph Nye recently noted, immigration reform “will be an important step in preventing the decline of American power.”

Many experts worry that America will be eclipsed by a rising China. Nye quotes Singapore’s former leader Lee Kwan Yew for the rebuttal: It won’t happen because America draws the world’s best and brightest and grants them the freedom to pursue their dreams.

Here’s hoping the fragile bipartisan effort in Washington succeeds in enacting a good reform bill.