Candidates for an open US Senate seat in New Mexico are parrying a barrage of political attack ads with the first televised debate of the campaign scheduled for Monday evening. Retiring Democratic Sen. Tom Udall has endorsed as his successor allied six-term US Rep. Ben Ray Luján, while Republican former television meteorologist Mark Ronchetti is promising to chart a more conservative political course on issues from health care to economic recovery. Absentee balloting begins Tuesday across the state that currently has an all-Democratic delegation to Washington, D.C. New Mexico hasn’t backed a Republican for Senate since 2002, and Trump lost New Mexico in 2016 to Hillary Clinton by 8 percentage points. Scientist and Libertarian Party candidate Bob Walsh also was expected to join the debate in his no-frills bid for Senate without a federally registered finance committee.