The three top Republican challengers to Utah Rep. Jim Matheson are all within 6 points of the six-term Democrat, according to a poll taken a week before the state GOP’s nominating convention.

Matheson, one of the most vulnerable incumbents in the country, led former state Rep. Carl Wimmer 46 percent to 45 percent, Saratoga Springs Mayor Mia Love 45 percent to 42 percent, and former state Rep. Stephen Sandstrom 47 percent to 41 percent. The poll of 625 likely voters, conducted by Mason-Dixon Polling and Research for the Salt Lake Tribune, was taken April 9-11 and had a 4-point margin of error.

Matheson’s GOP challengers will face off April 21 at the state party convention. A candidate can win the nomination with 60 percent of the 4th district delegate vote, otherwise the top two finishers will run in the June 26 primary.

Matheson’s re-election was complicated by a GOP-controlled redistricting. He opted to run in the Salt Lake County-based 4th district, which gives him his best shot at returning to Congress for a seventh term. The district leans Republican — Sen. John McCain (R-Ariz.) would have won 56 percent there in 2008 — and includes only about a quarter of Matheson’s current district.