WASHINGTON — Republicans in the Senate have killed legislation sponsored by President Barack Obama to spend $60 billion on building and repairing roads, rail lines and other infrastructure to help kick-start the sluggish economy.

The 51-49 vote fell well short of the 60 votes required under Senate procedures to start work on the bill. The infrastructure measure is the third in a string of Senate defeats for Obama’s stimulus-style jobs agenda, which would be financed by a tax surcharge on the very wealthy.

Despite the repeated losses, Democrats seem to think they’ve found a winning issue in pressing popular ideas from Obama’s poll-tested jobs package. Republicans counter that the president is more interested in picking political fights than in seeking compromise.