Bob Barr

An L.A. Times/Bloomberg poll released Tuesday shows U.S. Sen. Barack Obama (D-Ill.) beating U.S. Sen. John McCain (R-Phoenix) by 12 points in a head-to-head nationwide matchup, and by 15 if third party candidates Ralph Nader and Bob Barr are included, according to a report in the L.A. Times.

The poll comes days after a Newsweek poll found a 15 point advantage for Obama among voters across the country. Both polls found evidence of an "enthusiasm gap" between the candidates:

"McCain suffers from a pronounced 'enthusiasm gap,' especially among the conservatives who usually give Republican candidates a reliable base of support. Among voters who describe themselves as conservative, only 58% say they will vote for McCain; 15% say they will vote for Obama, 14% say they will vote for someone else, and 13% say they are undecided.

By contrast, 79% of voters who describe themselves as liberal say they plan to vote for Obama.