An internal poll shows Nevada Rep. Dina Titus in a tight race against Sen. Dean Heller if she decides to challenge him in 2018.

The 1st District Democratic congresswoman is mulling a run against the vulnerable Republican, but would have to first face off against Rep. Jacky Rosen of the 3rd District in a primary.

Heller led Titus 47 percent to 45 percent, within the poll’s 4-point margin of error, the Las Vegas Review-Journal first reported. 

Titus’ campaign paid Anzalone Liszt Grove Research, a public opinion firm, to conduct the survey of 600 likely voters in June. The group worked for President Barack Obama’s 2008 and 2012 campaigns, polling in nine states, including Nevada.

Heller has been the subject of heavy criticism from Democrats both in Washington and Nevada over the course of the Senate’s attempt to repeal and replace the 2010 health care law. He is the only Republican senator up for re-election next year in a state won by Democrat Hillary Clinton last fall.

Rosen, who formally announced her challenge to Heller earlier this month, is backed by former Senate Democratic leader Harry Reid. A freshman congresswoman from the Las Vegas suburbs, she said Reid encouraged her to get in the race.

Titus used the polling results to push back against Reid’s preference for Rosen.

“These figures dispel the Reid myth that I am not competitive in a statewide race,” she said in a statement.

If Titus does decide to run, it would be the third time she’s faced an opponent chosen by Reid. She went up against then-Henderson Mayor Jim Gibson in a 2006 gubernatorial primary. Gibson was backed by Reid, but Titus defeated him and then narrowly lost in the general election.

In 2012, Reid supported his former intern and then-state Sen. Ruben Kihuen for the 1st District House seat. Titus ran for the seat anyway and Kihuen later dropped out. He now represents Nevada’s 4th District.

Titus said she would decide on whether she would challenge Heller “after spending time in the district during the month of August.”

Inside Elections with Nathan L. Gonzales rates the Nevada Senate race a Toss-up.

Correction 1:42 p.m. | An earlier version of this story misstated the result of the 2012 Democratic primary in Nevada’s 1st District.