By nominating Loretta Lynch for U.S. attorney general, President Barack Obama has given the new Republican Senate majority an opportunity to avoid picking a partisan fight. The GOP should seize it.

In two stints as U.S. attorney for the Eastern District -- including Brooklyn, Queens and Staten Island -- Lynch has proved herself a tough, effective prosecutor who, barring unexpected revelations, is eminently qualified. The Harvard-educated lawyer has handled terrorism, civil rights and public corruption cases. By appointing the low-key, twice-confirmed, nonpolitical professional, Obama has offered Republicans the chance to get their fragile relationship off to a pragmatic start.

In that spirit, they also need to quickly agree on the next U.S. attorney for the Eastern District. Since 9/11, this U.S. attorney's office has notched more terrorism convictions than any other in the country, including putting away the people responsible for al-Qaida's 2009 plot to attack the subways. If Lynch moves up, the office needs a strong hand to guide that work, along with sensitive cases such as the tax fraud prosecution of Rep. Michael Grimm of Staten Island.

Unfortunately, rather than simply debate Lynch's qualifications, Republicans have signaled they'll turn her confirmation into a proxy war over the president's power to bypass Congress on immigration. If House Republicans continue to block reform, Obama will use executive orders to allow some people who are here illegally to remain and work. That's sure to boil the bad blood between the two parties. Exploring Lynch's analysis of the legality of such presidential action would be appropriate, but breaking ranks with Obama shouldn't be the bar for confirmation.

The GOP and Obama need to resolve their immigration fight without making collateral damage of a superb nominee for attorney general.