Joni ErnstJoni Kay ErnstKimmel writer tweets amount NRA has given lawmakers in response to shooting prayers Both sides of immigration fight unhappy with Senate debate White House plays defense after FBI testimony MORE appears to be well on her way to becoming the Republican pick to replace the retiring Sen. Tom Harkin (D-Iowa), according to a new poll.

Ernst enjoys twice as much support among primary voters as her closest competitor, according to survey data released Sunday from the Des Moines Register.

The publication’s poll found Ernst enjoying 36 percent support from likely GOP voters. Businessman Mark Jacobs is the closest GOP contender, pulling only 18 percent support.

If those numbers hold, Ernst would be able to lock up the party’s nomination on Tuesday without heading to a run-off — 35 percent is needed to win the state’s primary.

With two days to go, there are still 16 percent of likely primary voters who remain undecided. But Ernst enjoys broad support across all demographics and across the state. The winner of the party’s primary will likely face off against Rep. Bruce Braley, the leading Democrat to replace the long-serving Harkin.

While some GOP races have seen heated splits between establishment forces and conservative upstarts, a broad swath of Republican powers have rallied around Ernst in her race. The Iraq war veteran has earned endorsements from both Sarah Palin and Mitt Romney.

On Monday, Sen. Marco Rubio (R-Fla.) will head to the state to campaign on her behalf.

Former U.S. attorney Matt Whitaker, despite backing from GOP Texas Gov. Rick Perry, only pulled 13 percent support in Sunday’s poll. And former Air Force pilot Sam Clovis stands at 11 percent, compared to just 2 percent for Navy veteran Scott Schaben.