WASHINGTON — Congressman Jerry McNerney, a freshman Democrat, has emerged as one of the Republicans' top targets in Congress this year, making the race in his district that rarity in California politics — a national battleground contest and a true tossup. In 2006, McNerney pulled off one of the big upsets of the year when he knocked off Republican Richard Pombo, a committee chairman who earned the ire of environmental groups. Now, efforts by the GOP to retake the district, which stretches from Stockton through Alameda County to Morgan Hill, ensures an expensive campaign and should be one of the...