(CNN) - Former Democratic congressman Harold Ford, Jr. has decided to pass on a bid to unseat Sen. Kirsten Gillibrand, D-New York.
Gillibrand was appointed last year by New York Gov. David Paterson to replace Hillary Clinton, who stepped down to become secretary of state. The Democratic establishment has lined up behind Gillibrand, effectively clearing the field of any primary challengers who might have been thinking about taking on the freshman senator.
But Ford recently emerged as a possible challenger to Gillibrand, who previously represented a congressional district in upstate New York.
The Tennessee Democrat, who moved to New York City in 2006 after losing a Senate race against Bob Corker, explained his decision not to mount a primary challenge to Gillibrand in an op-ed published on the New York Times Web site Monday.
"I've examined this race in every possible way, and I keep returning to the same fundamental conclusion: If I run, the likely result would be a brutal and highly negative Democratic primary - a primary where the winner emerges weakened and the Republican strengthened.
"I refuse to do anything that would help Republicans win a Senate seat in New York, and give the Senate majority to the Republicans."
A Ford confidante was more blunt. "He wasn't going to be responsible for a Massachusetts-style surprise in New York," the source said, referring to Democrats' recent upset loss of the Senate seat held for more than four decades by the late Edward Kennedy.
The Gillibrand campaign was quick to respond to Ford's announcement.
"No matter who her opponent is this fall," Gillibrand spokesman Glen Caplin said in a statement, "she will wage a vigorous campaign on her strong record and her vision for New York."