President Obama's 15-point advantage over Mitt Romney in Massachusetts could kill rookie Sen. Scott Brown's bid to beat back Democratic challenger Elizabeth Warren, according to several polling experts and key Republican analysts.

While Brown remains popular, the likelihood that Democrats backing Obama won't split enough tickets has Republicans glumly considering Massachusetts a loss, and the result is that without Brown's reelection they probably won't win control of the Senate.

Larry Sabato, Kyle Kondik and Geoffrey Skelley of the University of Virginia's Center for Politics, are the most recent pundits to shift the Senate seat to "leans Democratic." They credit Obama's polling over Romney, himself a former Massachusetts governor. The trio also noted that Brown would have to receive some 300,000 votes from Obama voters to survive.