Some Republicans, including state GOP chairman Tony Sutton, were hoping Pawlenty would get right back into the ring and take on freshman Democratic Sen. Amy Klobuchar next year.
"I don't know what I will be doing next," Pawlenty said in an email to The Associated Press. "However, I will not be running against Amy in 2012."
While still a presidential candidate last week, Pawlenty told the Star Tribune of Minneapolis he didn't have interest in the Klobuchar race. But Republicans saw a renewed chance to recruit him after he left the presidential race Sunday.
Pawlenty, 50, ended his campaign after finishing third in an Iowa Republican straw poll. He had spent many months and millions building his campaign following two terms as Minnesota governor.
Sutton said Monday he planned to give Pawlenty time to decompress before making his Senate pitch.
"I think he'd be a heck of a candidate for U.S. Senate," Sutton said.
Republican leaders are trying to build a field of possible rivals to Klobuchar, who has strong public approval ratings and more than $3 million stocked up so far.
Former state Rep. Dan Severson is the only Republican to step forward. He was the party's unsuccessful nominee for secretary of state in 2010.