Associated Press

A group of tea-party and conservative organizations urged Sen. Lamar Alexander (R., Tenn.) to retire rather than seek a third term next year, signaling that tea-party activists have zeroed in on a new target as they try to pressure incumbent Republicans from the right.

In an open letter published Wednesday, 20 groups based in the state attacked Mr. Alexander, saying the country “can no longer afford compromise and bipartisanship, two traits for which you have become famous.”

The letter was signed by several groups purporting to represent tea-party and conservative activists in a number of counties across Tennessee. According to Matt Collins, an activist who said he wrote and circulated the letter, the groups collectively represent around 10,000 members…