Tom Emmer said Friday that he would withdraw thousands of ballot challenges deemed frivolous in order to speed the recount in the Minnesota governor’s race, but that he had not decided whether he would sue if he lost the election. Mr. Emmer, a Republican, had trailed the Democrat, Mark Dayton, by nearly 9,000 votes going into the recount, which began Monday. Mr. Emmer has been criticized for filing challenges that election officials complained were unfounded. With the recount nearly done, a state report listed 2,839 ballot challenges for Mr. Emmer and 35 for Mr. Dayton, who withdrew them Thursday.