In a statement from her campaign, Estabrook said that when she looked in the mirror Monday morning she noticed "the left side of my face was drooping slightly and I was losing control of my left arm."

The 63-year-old went to Monmouth Medical Center, near her Spring Lake home, where doctors confirmed she had suffered a stroke.

She reported she did not suffer long-term damage, but she noted it could happen again.

"Make no mistake, until Monday I was ready to fight for the Republican nomination and the chance to defeat (Democratic U.S. Sen.) Frank Lautenberg," she wrote. "I have never backed down from a fight and I am convinced we would have been successful."

From the Democrats' perspective, Estabrook was the most feared of the three Republican candidates because the wealthy developer was able to finance her own campaign and because she comes from the moderate wing of the Republican Party in this blue state.

She had already made subtle work of Lautenberg's age; academic polls have said voters think he is too old at 84 to seek another six-year term.

That theme was hit by GOP State Committee Chairman Tom Wilson this morning in reacting to Estabrook's withdrawal.

"Which candidate is best able to endure the rigors of a campaign and who is up for the demands of serving every day, for six years, to fight for New Jersey?" Wilson asked. "Senator Lautenberg is 84 years old and has served in the Senate for nearly 25 years. ... Frank Lautenberg had his chance and his best days, which really weren't very good, are behind him."

The two remaining GOP candidates are dentist and state Sen. Joe Pennacchio (R., Morris), and Murray Sabrin, a Ramapo College finance professor.