Running from Salt Lake County's northern border down to about 8000 South, this map would lump most liberal, Democratic areas together, instead of splitting them among different districts.
Matheson, a six-term Democrat, has faced criticism from liberals who complain he is too moderate and who could launch a convention or primary challenge.
"I mean look at his last election. He was forced into a primary by the left," Sumsion said.
Claudia Wright won 45 percent of the vote at the 2010 Democratic State Convention to force a primary election, which Matheson went on to win by a more-than-comfortable 68-32 margin. But Wright had little money, raising just $39,000 compared to the $1.8 million that Matheson raised overall.
Michael Picardi, former campaign manager for Wright and co-founder of the Coalition of Utah Progressives, said the convention outcome could have been different if Wright and Matheson faced each other in a "doughnut hole" instead of the current vast, more moderate district. "She would have done much better," he said.
So, Picardi agrees with Sumsion that the doughnut hole could make Matheson vulnerable. "I believe Matheson has moved so far to the right that he doesn't represent the core values of the party. He would face a harder challenge from the left in Salt Lake County."
While a more-left candidate might win the Democratic nomination in the doughnut hole, winning the general election could still be difficult among all voters who tend to be more moderate than Democratic delegates.
Picardi said whether a left-leaning candidate could win the general election in the doughnut hole "depends on who is running in both parties," but acknowledges the battle could be hard-fought if a moderate Republican were running.
Matheson, through his spokeswoman, declined comment on Sumsion's latest map, and whether it could make him vulnerable from the left.
Sumsion, though, says he doesn't sense much support for the Democratic-style doughnut hole plan on the Redistricting Committee, where Republicans outnumber Democrats 14 to five.
If anything, he said he feels more support is forming for a "reverse doughnut" hole proposed by Senate President Michael Waddoups, R-Taylorsville, that would create one all-Salt Lake County district but in its conservative southern end. That plan would join most Democrats in northern Salt Lake County areas with conservative, southern Utah areas.
Sumsion said he personally would like to have an urban-rural mix in all four U.S. House districts in Utah, saying he feels that would help in Utah's struggles with the federal government over public lands issues.
He has drawn some "pizza slice" proposals that would split Salt Lake County into three or four pieces, combining each with rural areas. Democrats have complained that could dilute their votes in their one stronghold statewide, and hurt the chances of reelecting Matheson or electing another Democrat. Upcoming redistricting hearings
The Redistricting Committee has two field hearings on July 9. One is in Moab at 11 a.m. at the Grand County High School auditorium, 608 S. 400 East. The other is in Price at 4 p.m. at the Carbon County Events Center, 450 S. Fairgrounds Way.