ST. PAUL  The vote gap between the two candidates in Minnesota’s still-undecided Senate race  the longest, closest and costliest in state history  has narrowed since Election Day, but the hostility and vitriol surrounding the race seem to grow by the hour.

A record 2.9 million Minnesotans went to the polls on Nov. 4. Unofficial returns the next morning showed the incumbent Republican senator, Norm Coleman, with a 725-vote lead over his Democratic challenger, the comedian Al Franken. Since then, as county canvassers certified results and election errors were corrected, that lead dwindled to 206 votes, seven-thousandths of 1 percent.

Overlooked absentee ballots have favored Mr. Franken. For example, 55 absentee ballots from Ramsey County were not added until Nov. 5, with 33 going to Mr. Franken, county election officials said. On Thursday, Mr. Franken’s campaign filed a lawsuit for access to data on voters in the county whose absentee ballots were rejected. The campaign hopes a legal victory could unlock this information statewide, a spokesman said.

Stakes are high because with three Senate races yet to be decided, Democrats still have a chance of winning the 60 seats needed to break Republican filibusters in Washington.